AISC
A way of adding up almost everything it costs to produce one unit of a metal — not just the day-to-day running costs but also the spending needed to keep the mine going into the future.
Technically: All-In Sustaining Cost is a metric developed to give a fuller picture of the cash cost of production than simple cash-cost or C1-cost figures. It adds sustaining capital expenditure, corporate general and administrative costs, and often reclamation accruals to the direct operating cost, but excludes expansion capital and financing costs. AISC is most widely used in gold and silver reporting, where it was formalised by the World Gold Council, though the precise scope of inclusions varies between companies, which limits strict cross-company comparison.
Markets
Bayer process
The standard industrial method for purifying bauxite ore into alumina powder, using hot caustic soda to dissolve the aluminium and leave the impurities behind.
Technically: The Bayer process is the dominant commercial route for producing metallurgical-grade alumina from bauxite, comprising four principal stages: digestion of crushed bauxite in hot concentrated sodium hydroxide solution to dissolve aluminium-bearing minerals as sodium aluminate; clarification and washing to separate the insoluble residue (red mud or bauxite residue); precipitation of aluminium hydroxide from the cooled, seeded liquor; and calcination of the hydroxide to anhydrous alumina. The process is selective for gibbsite, boehmite and diaspore but is less effective on silica-rich bauxites because silica reacts with caustic to form desilication products that consume reagent and reduce yield.
Processing
HPAL
A process that uses a pressurised vessel filled with very hot, oxygen-rich acid to dissolve nickel and cobalt out of a type of ore that is otherwise hard to treat.
Technically: High-pressure acid leach is an autoclave-based hydrometallurgical process in which laterite ore is leached with sulfuric acid at elevated temperature and oxygen partial pressure, conditions that dissolve nickel and cobalt selectively relative to iron. The high operating temperature is necessary because nickel-bearing minerals in limonite and saprolite laterites are insufficiently reactive under atmospheric leach conditions. HPAL is distinguished from atmospheric heap or vat leaching not merely by pressure but by the consequent change in iron chemistry: at HPAL conditions, dissolved iron precipitates as hematite within the autoclave rather than contaminating the pregnant liquor.
Processing
Hall-Héroult process
The only widely used method for making aluminium metal, passing electricity through dissolved alumina to split it into molten aluminium and carbon dioxide gas.
Technically: The Hall-Héroult process is the electrolytic reduction of alumina dissolved in molten cryolite (sodium aluminium fluoride) at around 960 °C, in which direct current causes aluminium ions to deposit as liquid metal at the carbon cathode while oxygen is discharged at the carbon anode, reacting with the anode to produce carbon dioxide. It is an energy-intensive operation; electricity is the dominant operating cost and the largest contributor to the carbon footprint of primary aluminium production. The process is occasionally confused with electrorefining, but Hall-Héroult produces primary metal from an oxide feedstock rather than purifying a crude metal anode.
Processing
JORC
A set of rules used mainly in Australia that tells mining companies how they must measure and report what minerals they have found.
Technically: The JORC Code (Joint Ore Reserves Committee Code) is the Australasian standard for public reporting of exploration results, mineral resources and ore reserves. It is a principles-based code requiring that all public statements be based on work done by or under the supervision of a qualified person. JORC is the mandatory reporting framework for companies listed on the Australian Securities Exchange and several other regional exchanges, and its resource and reserve categories are broadly equivalent to, though not identical with, those defined under NI 43-101 and other international codes.
Markets
Kroll process
The standard way of making titanium metal, replacing titanium's bond to chlorine with a bond to magnesium and then separating the result to leave spongy titanium metal.
Technically: The Kroll process is a batch pyrometallurgical reduction in which titanium tetrachloride vapour is reacted with liquid magnesium metal in a sealed, inert-atmosphere retort to yield titanium metal and magnesium chloride; the magnesium chloride is then drained and the residual magnesium recovered by vacuum distillation, leaving a porous titanium mass known as sponge. The process remains the predominant industrial route for primary titanium despite its batch nature and high energy demand, because titanium's extreme reactivity toward oxygen and nitrogen at elevated temperature makes continuous melting or aqueous routes difficult to implement at commercial scale. The magnesium chloride by-product is typically electrolysed to regenerate both magnesium and chlorine for recycle.
Processing
LCE
Short for Lithium Carbonate Equivalent — a standard unit used to say how much lithium is in something by imagining it has all been turned into lithium carbonate, the most common traded form.
Technically: LCE, lithium carbonate equivalent, is a normalising convention that expresses any quantity of lithium — whether in ore, brine, spodumene concentrate, lithium hydroxide or metallic form — as the equivalent mass of lithium carbonate (Li₂CO₃) it would yield. Because lithium can be sold as carbonate, hydroxide or metal, and resources can be reported as contained lithium or various compounds, LCE provides a common basis for comparison across the supply chain. Converting between LCE and contained lithium metal, or between LCE and lithium hydroxide equivalent, requires applying the relevant molar mass ratios; failing to do so is a frequent source of inconsistency in market reporting.
Materials
NI 43-101
A Canadian rulebook that sets out exactly how mining companies must tell the public what they have found in the ground.
Technically: National Instrument 43-101 is a Canadian securities regulation that governs the disclosure of scientific and technical information about mineral projects to the public. It requires all technical disclosures to be prepared by or under the supervision of a qualified person as defined in the instrument, and it mandates specific report formats for resource and reserve estimates. Companies listed on Canadian exchanges must comply with NI 43-101; its definitions of resource and reserve categories are aligned in structure with JORC and the CRIRSCO family of codes, though procedural and disclosure requirements differ in detail.
Markets
PEA
An early, rough-and-ready estimate of whether a mineral project might be worth developing, before anyone has done the detailed engineering work.
Technically: A Preliminary Economic Assessment is a study that includes an initial assessment of the potential viability of a mineral deposit, typically completed at an order-of-magnitude level of cost accuracy and before a pre-feasibility study. Uniquely among the study levels, a PEA is permitted under most reporting codes to incorporate inferred resources in its economic analysis, provided appropriate caveats are disclosed. Because of its lower engineering maturity and the inclusion of less-certain resource categories, a PEA cannot be used to support a reserve declaration or a production financing decision.
Markets
REO
Short for Rare Earth Oxides — a way of measuring and reporting the total amount of rare-earth elements in a sample by expressing them all as their oxide forms added together.
Technically: REO, or total rare earth oxide, is the standard reporting unit for rare-earth content in resources, concentrates and products, expressing the sum of individual rare-earth element oxides on a weight-percentage basis. Because each element is reported as its stoichiometric oxide rather than as the free metal, REO figures are systematically higher than total rare earth element (TREE) figures for the same material; the conversion factor differs for each element. REO is sometimes used interchangeably with TREO (total rare earth oxide), and both should be distinguished from TREE, REE and contained-metal figures, as mixing conventions without conversion produces material accounting errors.
Materials
SX-EW
A way of pulling copper out of a liquid using special chemicals, then using electricity to turn it into pure sheets of metal — no smelting needed.
Technically: Solvent extraction–electrowinning is a two-stage hydrometallurgical route in which a pregnant leach solution is contacted with an organic extractant to selectively concentrate the target metal into a loaded organic phase (solvent extraction), which is then stripped and fed to an electrowinning cell where the metal deposits onto a cathode. In copper production it is most commonly paired with heap or dump leaching of oxide or secondary sulfide ores. It is sometimes conflated with electrorefining, but electrorefining purifies an already-cast anode whereas electrowinning deposits metal directly from solution.
Processing
Siemens process
A method of making very pure silicon by decomposing a silicon-containing gas onto hot rods and gradually building up thick rods of high-purity silicon.
Technically: The Siemens process produces polycrystalline silicon of semiconductor or solar-cell grade by the chemical vapour deposition of trichlorosilane — or, in some variants, silane — onto electrically heated silicon slim rods in a sealed reactor, with hydrogen as the carrier and reducing gas; silicon deposits progressively on the rod surface until rods of the required diameter are harvested. It is distinguished from metallurgical-grade silicon production, which uses carbothermic reduction in an electric arc furnace and yields a far less pure product. The process is energy-intensive and generates tetrachlorosilane as a significant by-product, the handling and recycling of which has a material effect on overall process economics and environmental performance.
Processing
acid mine drainage
Acid mine drainage is water that turns acidic after flowing through broken rock that contains certain sulfur minerals. This acidic water can carry dissolved metals into rivers and streams, harming the environment.
Technically: Acid mine drainage (AMD) is the low-pH, metal-laden water produced when sulfide minerals — most commonly pyrite — are exposed to oxygen and water, generating sulfuric acid through a combination of chemical and bacterially mediated reactions. AMD can arise from active workings, waste-rock dumps, tailings facilities or abandoned workings, and its generation may continue for decades or centuries after mining ceases. It is distinguished from neutral mine drainage in that the acid load exceeds the neutralising capacity of the surrounding rock and water, enabling the mobilisation of iron, manganese and a range of heavy metals at concentrations that can be acutely toxic to aquatic systems.
Mining
adit
A horizontal tunnel driven directly into the side of a hill or mountain to reach ore underground, so that water and broken rock can drain or roll out naturally without being lifted.
Technically: A horizontal or near-horizontal entry driven from the surface into a hillside or cliff face to provide access to underground workings, with the primary advantage that it allows natural gravity drainage of groundwater and, in some configurations, gravity tramming of ore. An adit differs from a decline in that it is essentially flat rather than inclined, and it differs from a shaft in being horizontal rather than vertical. In hilly or mountainous terrain, adits can give access to multiple levels if the topography permits entry points at different elevations. The term is sometimes loosely applied to any horizontal underground opening, but in precise usage it refers specifically to an opening that intersects the surface.
Mining
anode
The impure block of metal that slowly dissolves away during electrorefining. Electricity pulls metal atoms off it and deposits them, in purified form, onto the cathode on the other side of the tank.
Technically: In electrorefining, the anode is the positively charged electrode, cast from blister or fire-refined copper, that undergoes oxidative dissolution as the current drives metal ions into solution. Its composition determines which impurities accumulate in the electrolyte and which collect as anode slime beneath or around it. The term is also used in electrowinning, but there the anode is an inert or dimensionally stable electrode that does not dissolve; confusing the two contexts matters because anode behaviour and anode slime generation are specific to electrorefining only.
Processing
anode slime
A muddy residue that collects under the dissolving anode during electrorefining. It contains impurities and sometimes valuable materials such as silver and gold that did not dissolve into the liquid.
Technically: Anode slime is the solid residue that accumulates at the base of the anode or on the cell floor during copper electrorefining, composed of anode constituents that are insoluble under the operating conditions of the electrolyte—typically selenium, tellurium, lead sulfate, and the precious metals silver, gold, and platinum-group elements. Recovery of these by-products from anode slime is often an economically significant part of a copper refinery's operation. The composition and quantity of anode slime are direct functions of the anode chemistry, making anode quality control important for by-product recovery planning.
Processing
anomaly
An anomaly is a spot where a measurement — such as the strength of a magnetic field or the amount of a metal in soil — is noticeably different from the surroundings, suggesting something unusual might lie underground.
Technically: In exploration geology, an anomaly is a statistically significant departure from the local or regional background value of a measured parameter, whether geochemical, geophysical, or remote-sensing derived, and it forms the basis for prioritising drill targets. Not all anomalies reflect economic mineralisation; many result from barren lithological contrasts, instrument artefacts, or surficial contamination, which is why anomaly follow-up always involves additional lines of evidence before drilling is committed. The term should be qualified by its type and the method that detected it — for example, a soil geochemical anomaly differs fundamentally in its implications from a magnetic anomaly even if both occur in the same area.
Geology
apparent consumption
An estimate of how much of a material a country uses, calculated from production and trade figures rather than from measuring what each factory actually consumes.
Technically: Apparent consumption is calculated as domestic primary production plus imports minus exports, with an adjustment for changes in reported inventory levels where such data are available. It is described as 'apparent' because it is derived from supply-side statistics rather than measured at the point of end use, meaning it includes any unrecorded stockbuilding or drawdown. Apparent consumption is the standard proxy for demand in national and global commodity balances and feeds directly into the calculation of net import reliance. It can diverge significantly from true consumption when stock changes are large, unreported, or estimated with low accuracy.
Markets
artisanal mining
Artisanal mining is small-scale mining done by individuals or small groups using simple hand tools rather than large machinery. It is common in many parts of the world and is how some communities make a living.
Technically: Artisanal and small-scale mining (ASM) refers to informal or semi-formal mining conducted by individuals, families or small cooperatives using predominantly manual methods and limited mechanisation, typically without the permits, capital investment or technical infrastructure of industrial operations. The term encompasses a wide spectrum of formality: some ASM operators work within legal frameworks, others in de facto legal grey areas, and others outside any regulatory system entirely. ASM is distinguished from small-scale industrial mining chiefly by the absence of systematic geological assessment, engineered mine design and formal employment structures, rather than by any fixed threshold of tonnage or output.
Mining
assay
An assay is a chemical test that measures exactly how much of a valuable mineral or metal is present in a piece of rock, the way a cook might weigh out exactly how much sugar is in a recipe.
Technically: An assay is a quantitative analytical procedure applied to a rock, soil, or water sample to determine the concentration of one or more elements or minerals, reported in units such as grams per tonne or percentage by mass. In resource estimation, assay results are the primary input to grade calculations and must be traceable to certified reference materials and blanks to be defensible. Assay is sometimes loosely used to mean the result itself rather than the procedure; technical reports treat these as distinct.
Geology
assessed price
A price that a specialist reporting agency works out by collecting information about real deals and published offers, then publishing its best estimate of what the commodity is worth that day.
Technically: An assessed price is produced by a price reporting agency (PRA) — such as Fastmarkets, Platts or Argus — using a defined methodology that aggregates transaction data, bids, offers and broker quotes over a fixed assessment window, typically the end of a trading day. Because many commodity markets are opaque and transactions infrequent, the assessment reflects the PRA's methodology as much as the raw market; different agencies applying different criteria to the same market can publish different numbers. Assessed prices are routinely embedded in physical supply contracts as the pricing reference, which makes the methodology and its governance commercially significant. They are distinct from exchange-settled prices, which derive from standardised, centrally cleared contracts.
Markets
autoclave
A sealed, pressurised vessel that lets water be kept much hotter than its normal boiling point, so that reactions happen faster or at all.
Technically: In metallurgical processing an autoclave is a pressure vessel in which aqueous leaching is conducted at elevated temperature and partial pressure of oxygen or steam, allowing solution temperatures well above the atmospheric boiling point of water and enabling oxidation or dissolution reactions that are thermodynamically or kinetically impractical at ambient pressure. The term describes the vessel itself, though it is commonly used as shorthand for the pressure-leach operation performed within it. It should not be conflated with a simple heated leach tank; the defining characteristic is that the system operates above ambient pressure, which fundamentally alters both the chemistry and the engineering requirements.
Processing
backfill
Backfill is material packed back into the empty spaces left after underground mining. It stops the ground from collapsing and can allow miners to safely dig out the next section nearby.
Technically: Backfill is any material placed into mined-out stopes or other underground voids to provide ground support and reduce surface subsidence. It is commonly categorised as hydraulic fill (slurried fine material pumped underground), paste fill (thickened tailings with binder), or waste-rock fill. In operations where cemented paste fill is used, the compressive strength of the cured fill is a design parameter that determines how close adjacent stopes may be mined, distinguishing backfill from simple void control into an active structural element.
Mining
banded iron formation
A very ancient layered rock made of alternating stripes of iron-rich minerals and silica, laid down on ancient seafloors long before there was much oxygen in the atmosphere.
Technically: A banded iron formation (BIF) is a chemically precipitated sedimentary rock characterised by alternating iron-rich layers (typically magnetite or hematite) and silica-rich layers (chert), deposited predominantly in Precambrian marine basins. The banding is thought to reflect periodic changes in ocean chemistry or oxygen availability rather than clastic input. BIFs are the principal source rock for most of the world's iron ore, with economic deposits typically requiring secondary enrichment to raise iron grades to commercially workable levels.
Geology
base metal
The ordinary workhorse metals like copper, lead, zinc, nickel and tin that are mined and used in large quantities for everyday construction and manufacturing.
Technically: Base metals are those common non-ferrous metals that oxidise or corrode relatively readily when exposed to air or moisture, distinguishing them from precious metals. The group conventionally includes copper, lead, zinc, nickel, tin and aluminium, though precise membership varies by source. They are produced and traded in large volumes, and their prices are tracked as broad indicators of industrial activity. The term is primarily economic and commercial rather than chemical in its usage.
Materials
bench
One of the flat, step-like levels cut into the side of an open pit mine; the mine looks like a giant staircase when viewed from the air.
Technically: In open pit mining, a bench is a horizontal working level defined by a flat floor and a near-vertical face of rock — the bench face — cut to a specified height. Drilling and blasting are conducted at bench level, and excavation equipment works along the bench floor before the pit is deepened by creating the next bench below. Bench height, face angle, and the width of the horizontal berm between successive benches are determined by a combination of rock mass properties, equipment dimensions, and geotechnical stability requirements. The term is occasionally used in underground mining to describe a stepped working face, but without qualification it refers to an open pit feature.
Mining
benchmark price
A price that big buyers and sellers agree on — often once a year — which then sets the standard that smaller deals in that market copy.
Technically: A benchmark price is a reference price negotiated between major producers and consumers, historically in annual or quarterly contracts, against which other transactions in the same commodity are priced, often with a small adjustment for grade or location. It is most associated with iron ore and metallurgical coal, where a handful of large counterparties once set annual prices that the rest of the market adopted. The benchmark system has largely given way to index-linked pricing in iron ore, but the term persists and is sometimes loosely applied to any widely followed reference price, which can cause confusion with assessed or exchange-settled prices.
Markets
beneficiation
Beneficiation is everything done to raw dug-up rock to separate the useful mineral from the worthless rock around it, before the mineral is turned into a metal or chemical. Think of it as sorting and cleaning, not yet cooking.
Technically: Beneficiation encompasses the physical and physico-chemical unit operations—crushing, grinding, screening, gravity separation, flotation, magnetic separation, and drying, among others—applied to run-of-mine ore to produce a concentrate or other upgraded product suitable for downstream processing. It excludes smelting, refining, and leaching steps that alter chemical composition through heat or reagent reaction, though the boundary is contested in some regulatory and trade contexts. The term is sometimes used interchangeably with 'mineral processing', but in policy and trade literature 'beneficiation' often carries the broader sense of any value-adding step applied to a raw mineral commodity within a producing country.
Mining
beneficiation requirement
A government rule that says a country must do some processing on its own raw materials before sending them out — so that more of the value-adding work stays at home.
Technically: A policy instrument that obliges producers to carry out a defined level of mineral processing within the producing country before export is permitted. The threshold may be expressed in terms of minimum product grade, processing stage (concentrate, smelted metal, refined product) or value added. Beneficiation requirements are often confused with export controls, but the distinction matters: an export control restricts or bans the movement of a product, while a beneficiation requirement conditions export on the product first reaching a specified state of transformation.
Markets
blister copper
Copper that is nearly pure but still has small amounts of impurities trapped inside it. Its bumpy, blistered surface—caused by gas bubbles escaping as it solidifies—gives it its name.
Technically: Blister copper is the product of converting copper matte in a Pierce-Smith or similar converter, in which iron sulfide is progressively oxidised and slagged off, leaving a crude copper metal typically containing small but commercially significant quantities of sulfur, oxygen, and trace impurity metals such as gold, silver, arsenic, and bismuth. The characteristic blistered surface forms because dissolved sulfur dioxide escapes during solidification. Although high in copper content, blister copper requires fire refining and then electrorefining before it meets the purity specifications of cathode copper traded on commodity markets.
Processing
block caving
A method where miners cut away the rock supporting a large mass of ore so that it slowly collapses under its own weight, breaking into pieces that can then be collected from tunnels below.
Technically: A mass underground mining method in which a large column or block of ore is undercut, removing its support so that the overlying rock mass fractures and caves progressively downward under gravity. The broken material flows into draw points — funnel-shaped openings at the base of the cave — from which it is loaded and transported. Block caving is associated with very large, low-grade, roughly equidimensional orebodies, because its economics depend on extremely high throughput; the method is not selective and dilution from waste rock caving alongside ore must be managed carefully.
Mining
brine
Water with a very high concentration of dissolved salts — much saltier than seawater. Underground brines in certain deserts contain lithium, potassium, and other elements that can be extracted commercially.
Technically: Brine is an aqueous solution with a total dissolved solids concentration substantially above that of seawater, typically formed by the dissolution of evaporite minerals or by long-term evaporative concentration of meteoric or volcanic waters in closed basins. In the context of mineral resources, the term refers specifically to subsurface or surface-ponded waters exploited for their content of lithium, potassium, boron, magnesium, or bromine. Brine differs from seawater not only in concentration but often in ionic ratios, which determine the processing route required; a high magnesium-to-lithium ratio, for instance, significantly complicates selective lithium recovery.
Geology
brownfield
A brownfield project is one carried out near or around an existing or former mine, where some rock has already been studied and some infrastructure already exists, giving explorers a head start.
Technically: A brownfield exploration or development project operates in the proximity of an existing or previously mined deposit, benefiting from existing geological data, drill results, metallurgical knowledge, and often surface infrastructure such as roads, power, or processing facilities. Targeting in brownfield settings typically focuses on extensions of known mineralisation or satellite deposits within established geological corridors, which reduces some categories of exploration risk while introducing others, such as sterilised ground, legacy contamination, and tenure complications. Brownfield should not be confused with the environmental planning term of the same name, which refers to previously developed urban land; the mining usage is geological and logistical in scope.
Geology
by-product
Something useful that comes out of a factory or mine alongside the main product, but which was not the main reason for running the operation.
Technically: A by-product is a saleable material recovered during the processing of a primary commodity, where the economics of the operation are driven by that primary commodity rather than by the by-product. The distinction matters in cost accounting: a by-product's revenue is typically credited against the cost of the primary product rather than allocated as a separate cost centre, and production volume is constrained by primary output rather than by its own demand.
Materials
calcination
Heating a mineral strongly enough to drive off gases — often water vapour or carbon dioxide — without actually melting it.
Technically: Calcination is a thermal treatment carried out below the fusion point of the material, with the primary purpose of driving off volatile components such as chemically bound water, carbon dioxide or sulfur dioxide, thereby transforming the feed into a more reactive or chemically altered solid product. It is routinely confused with roasting: the distinction is that calcination targets decomposition or dehydration rather than oxidation of a sulfide or other reactive species. In the Bayer process, for example, aluminium hydroxide is calcined to produce anhydrous alumina.
Processing
capex
The large, upfront sums of money spent to build a mine or processing plant before it starts producing anything.
Technically: Capital expenditure, universally abbreviated to capex in the mining industry, refers to spending on physical assets required to bring a project into production or to sustain and expand an existing operation. In project evaluation it is divided into initial capex, covering construction to first production, and sustaining capex, covering ongoing asset replacement and expansion over the mine life. The accuracy of capex estimates improves through the study hierarchy from PEA to feasibility study; overruns in capex relative to feasibility-study estimates are one of the most common causes of project economics deteriorating between sanction and commissioning.
Markets
carbonatite
A rare type of volcanic rock made mostly of carbonate minerals — the same family as limestone — rather than the silicate minerals found in ordinary igneous rocks. Some carbonatites are important sources of rare-earth elements and niobium.
Technically: Carbonatite is an igneous rock, intrusive or extrusive, containing more than fifty percent carbonate minerals by volume, typically calcite, dolomite, or ankerite. It is genetically distinct from carbonate sedimentary rocks and from carbonated hydrothermal veins. Carbonatites are economically significant as hosts for niobium, rare-earth elements, phosphate, fluorite, and occasionally copper, and they are often associated with alkaline silicate intrusions in continental rift settings. The distinction from a marble or a hydrothermal carbonate vein rests on demonstrating an igneous origin through geochemistry and field relationships.
Geology
care and maintenance
Care and maintenance is when a mine has stopped producing but has not been permanently closed. The site is kept in a safe, working condition so that mining could start again if conditions improve.
Technically: Care and maintenance describes an operational status in which a mine has suspended production but maintains sufficient infrastructure, staffing and monitoring to preserve the physical and environmental integrity of the site and to allow restart without full recommissioning. It differs from closure in that no commitment to permanent cessation has been made and rehabilitation obligations are deferred. The status is typically adopted when commodity prices fall below the cash cost of production, when a key permit lapses, or when a resource owner is seeking to divest the asset; holding costs during care and maintenance are materially lower than full operating costs but are not zero.
Mining
cathode
The clean sheet of metal that pure metal grows onto during electrorefining or electrowinning. At the end of the process the cathode is the finished, high-purity product.
Technically: In electrometallurgy, the cathode is the negatively charged electrode onto which metal ions from the electrolyte are reduced and deposited as solid metal. In copper production the term 'cathode' is used both for the electrode itself during the process and for the flat, high-purity copper product that is sold after it is stripped from the starting sheet. Cathode copper is the standard tradeable form of refined copper and must meet published purity specifications to qualify for exchange-registered delivery; it is sometimes confused with the anode, which is the dissolving or oxidising electrode carrying the opposite charge.
Processing
cathode active material
The powder inside a battery's positive end that actually stores and releases electrical energy by holding onto lithium ions when the battery is charged.
Technically: Cathode active material (CAM) is the lithium-bearing oxide or phosphate compound that forms the electrochemically active component of the positive electrode in a lithium-ion cell, accepting and releasing lithium ions during discharge and charge respectively. Common CAM chemistries include lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminium oxide (NCA), and lithium iron phosphate (LFP), each with different trade-offs in energy density, thermal stability, and cycle life. CAM is distinct from the precursor cathode active material (PCAM) from which it is synthesised and from the finished electrode, which also contains binder, conductive carbon, and a current collector.
Processing
circularity
Designing systems so that materials keep being used again and again, rather than being thrown away after a single use — like a bottle that is refilled hundreds of times instead of discarded.
Technically: An approach to material flows in which the useful life of materials is extended through reuse, remanufacturing and recycling, reducing dependence on primary extraction. In minerals and metals analysis, circularity is measured in terms of collection rates, recycling rates and the proportion of secondary material that re-enters productive use at equivalent quality to primary material. It is important to distinguish circularity from recycling alone: circularity is a broader concept that encompasses design for disassembly, product life extension and closed-loop industrial systems, of which recycling is one component.
Markets
co-product
When a mine or factory produces two or more things at the same time and each one is important enough to help justify running the whole operation.
Technically: A co-product is a material recovered alongside another from the same ore body or process stream, where both contribute materially to the economic viability of the operation. Unlike a by-product, a co-product receives its own share of joint production costs rather than being treated as a credit. The boundary between co-product and by-product is contested and varies by accounting convention; in practice the distinction often turns on whether removing the secondary material would make the operation uneconomic.
Materials
comminution
Comminution means breaking rock into smaller and smaller pieces—first by crushing big lumps, then by grinding those pieces into a fine powder—so that the useful mineral grains become free from the surrounding rock.
Technically: Comminution is the collective term for all size-reduction stages in mineral processing, spanning primary crushing through to fine grinding, and its purpose is the liberation of valuable mineral particles from the host rock matrix at a particle size fine enough for effective separation. It typically accounts for the largest share of a concentrator's energy consumption, which makes comminution circuit design and efficiency central concerns in both plant economics and environmental assessment. The term encompasses crushing (above roughly a few millimetres product size) and grinding (below that threshold), and should be distinguished from classification, which is the separation of particles by size rather than their reduction—though the two operations are almost always conducted in close circuit with one another.
Mining
companion metal
A metal that hides inside the ore of a different, more common metal and can only be collected when that common metal is being processed.
Technically: A companion metal is one that occurs in ore principally as a trace constituent of another metal's mineral host rather than in economically minable deposits of its own, meaning its supply is structurally tied to the production decisions made for the host metal. Indium in zinc ores and tellurium in copper anode slimes are typical examples. Because a companion metal cannot be ramped up independently, its supply responds poorly to price signals, making it particularly susceptible to shortfalls when demand grows faster than host-metal production.
Materials
concentrate
The valuable mineral-rich material collected after processing ore. Think of it as the useful part that has been separated from most of the waste rock, ready for the next stage of treatment.
Technically: A concentrate is the product of a beneficiation step—commonly flotation or gravity separation—in which the grade of the target mineral or metal has been substantially raised relative to the run-of-mine ore, and most gangue has been discarded as tailings. Concentrates are defined by their contained metal grade and penalty element levels, which govern their commercial value and smelter treatment charges. The term is distinct from 'ore': ore refers to mineralised rock in the ground or as mined, while concentrate is an intermediate, processed product.
Processing
concentrator
A concentrator is a processing plant that takes crushed and ground ore and separates out the valuable mineral, producing a concentrate—a much smaller, richer portion—while the unwanted material goes to a waste pile called tailings.
Technically: A concentrator is a facility or integrated circuit of equipment whose primary function is physical or physico-chemical separation of valuable minerals from gangue, raising the grade of the target mineral to levels acceptable for smelting or hydrometallurgical treatment. The defining output is a concentrate—a product in which the valuable mineral is substantially enriched relative to the feed ore—alongside a tailings stream that contains the discarded gangue and process water. The term is sometimes used as a synonym for 'mill', but a concentrator is more precisely defined by its separation objective: a mill may perform grinding without achieving a saleable concentrate (for instance, when feeding a heap-leach pad), whereas a concentrator always produces one.
Mining
conflict mineral
A mineral that has been mined in a war zone and sold to help fund the fighting, in the same way that 'blood diamonds' became a well-known example.
Technically: A mineral extracted in a region of armed conflict where the proceeds of trade are reasonably understood to finance or benefit armed groups, whether state or non-state actors. The term carries a specific legal meaning under certain national legislations and due-diligence frameworks, which typically enumerate particular minerals and regions of concern rather than applying the category universally. It is important not to conflate the term with artisanal or small-scale mining in general, or with minerals produced in politically unstable regions that are not conflict-affected in the legal sense.
Markets
contained metal
The actual amount of useful metal sitting inside a quantity of ore or concentrate, not counting the rock, water or other waste wrapped around it.
Technically: Contained metal is the mass of a target metal element present in a stated quantity of ore, concentrate or other material, calculated by multiplying the total material mass by the assayed grade of that element. It is expressed in units of the pure metal, not the compound, unless stated otherwise. The term is important because commercial transactions and resource statements can report either contained metal or the weight of the physical material shipped; confusing the two — particularly when dealing with concentrates that may be only a fraction pure — is a common source of error in supply chain accounting.
Materials
conversion
A processing step that changes a material from one chemical form into another so it is ready for the next stage — like turning a metal ore into a gas that can be sorted by weight.
Technically: In the nuclear fuel cycle, conversion refers specifically to the chemical process by which uranium oxide concentrate (yellowcake) is purified and reacted to form uranium hexafluoride (UF₆), the gaseous compound required as feed for enrichment. Outside the nuclear industry the term is used more broadly for any stage that transforms a material into a chemically distinct intermediate suited to downstream processing, such as the conversion of ilmenite to synthetic rutile or titanium tetrachloride. The nuclear-fuel sense is the most precisely delimited and is the one most often intended when the word appears alongside 'enrichment' and 'yellowcake' without further qualification.
Processing
core sample
A core sample is a long cylinder of rock drilled out of the ground whole, like using a hollow cookie-cutter through layers of cake, so geologists can see the rock exactly as it sits underground.
Technically: A core sample is a continuous cylindrical section of rock recovered by a diamond or other rotary drill bit fitted with an annular cutting face, which preserves the original stratigraphy, structure, and mineralisation relationships along the drill path. Core recovery percentage — the proportion of the drilled interval actually retrieved — is recorded because incomplete recovery can bias grade estimates, particularly in friable or broken ground. Core differs from drill chips or reverse-circulation cuttings in that it retains orientation and intact fabric, making it the preferred sample type for structural logging and geometallurgical testwork.
Geology
cost curve
A chart that lines up all the world's mines for one commodity from cheapest to most expensive, so you can see which ones would shut down first if the price fell.
Technically: A cost curve ranks producing operations by their unit cost of production — typically C1 cash cost or AISC — plotted against their cumulative output, forming a step function that rises from left to right. The curve's shape reveals the industry's cost structure: a flat curve indicates producers are tightly clustered in cost, while a steep right-hand tail shows a small number of high-cost operations that are marginal at prevailing prices. The curve is widely used to assess where the price floor might settle in a downturn, on the assumption that producers to the right of the prevailing price are candidates for curtailment.
Markets
critical mineral
A mineral that a country or industry depends on heavily but might struggle to keep getting, either because it only comes from a few places or because there is no easy substitute for it.
Technically: A mineral is designated critical when two conditions coincide: supply is concentrated enough that a disruption is plausible, and there is no ready substitute for the material's function in key applications. Criticality is not a fixed property of the mineral itself; it is a relationship between supply geography, demand concentration and available alternatives, so a mineral may appear on one country's critical list but not another's.
Materials
current collector
A thin metal sheet inside a battery that gathers the electricity produced by the active materials and carries it to the battery's terminals — like a bus collecting passengers and delivering them to the station.
Technically: A current collector is a conductive substrate — typically a metal foil — onto which the active electrode material is coated or deposited, serving to gather electrons from across the electrode surface and conduct them with minimal resistance to the external circuit. In lithium-ion batteries, copper foil is conventionally used for the anode side and aluminium foil for the cathode side, the choice being governed by electrochemical stability at the respective operating potentials. Current collectors are sometimes overlooked in materials discussions because they are not electrochemically active, but their conductivity, thickness, and corrosion resistance directly affect cell efficiency and the overall mass loading of the finished cell.
Materials
cut-off grade
The lowest grade of rock that is still worth processing. Rock above the cut-off goes to the mill; rock below it is left behind or sent to the waste dump.
Technically: Cut-off grade is the minimum grade at which a unit of rock — a block, bench, or development heading — generates sufficient revenue to cover the cost of mining, processing, and selling. It determines the boundary between ore and waste and therefore controls both the size and the average grade of the reported resource or reserve. Because it is derived from cost and price assumptions, cut-off grade changes with commodity prices, exchange rates, and processing recoveries, which means the economic boundary of an orebody is not fixed.
Geology
decline
A sloping tunnel that winds downward from the surface into an underground mine, wide enough for trucks or conveyor belts to carry ore and equipment in and out.
Technically: An inclined tunnel driven from surface at a gradient sufficient to allow wheeled or tracked vehicles — typically diesel trucks or, in some operations, conveyor systems — to travel between the surface and underground working levels. Declines provide an alternative to shaft hoisting for accessing orebodies at moderate depth, with the advantage of lower initial capital cost and the flexibility to carry large equipment underground without the constraints of a hoisting conveyance. They are distinguished from adits by their significant downward inclination and from shafts by their drivable, ramp-like geometry. At greater depths, the travel time and fuel cost of trucking up a long decline typically make shaft hoisting more economical, which is why the two access methods are often compared directly in feasibility studies.
Mining
demand destruction
When prices rise so high, or a material becomes so hard to get, that buyers permanently stop using it and find other ways to do without — the demand does not just pause, it disappears.
Technically: A sustained and typically irreversible reduction in demand for a material resulting from price levels or supply constraints that have induced permanent changes in technology, behaviour or product design. Demand destruction differs from demand suppression, which is a temporary fall in consumption that reverses when conditions normalise; destruction implies that consumers have switched technologies or production processes in ways that do not simply unwind when prices ease. The concept is particularly relevant in minerals markets where prolonged price spikes can accelerate substitution or efficiency improvements that structurally lower the material intensity of key end uses.
Markets
dilution
Dilution is the extra worthless rock that gets mixed in with the ore when a mine is blasted and dug. The more dilution there is, the lower the overall grade of the material sent to the processing plant.
Technically: Dilution is the reduction in average grade of mined material caused by the incorporation of sub-cut-off-grade or waste rock into the ore stream during extraction. It is commonly expressed as the proportion of waste included in the ore parcel by mass or volume. Dilution is distinguished between planned dilution — unavoidable waste inclusion accounted for in the mine design — and unplanned dilution, which reflects over-break, wall sloughing or poor grade control. High dilution increases milling costs per unit of recovered metal and reduces head grade, directly affecting process economics.
Mining
doré
A rough bar of mixed gold and silver, still containing impurities, poured at a mine before being sent to a refinery to be separated and purified into pure metals.
Technically: Doré is an unrefined alloy of gold and silver, typically cast as bars at the mine or smelter following the processing of ore through leaching, gravity concentration, or pyrometallurgical routes. Its composition varies widely depending on the ore source, and it commonly contains minor quantities of base metals, sulfur compounds, and other impurities. Doré is the standard form in which gold and silver leave most mine sites for delivery to an independent bullion refinery, where the two precious metals are separated and brought to commercial purity; it is therefore a mine product and a refinery feed rather than a finished metal, and its value is assessed on the basis of assayed precious-metal content less refining charges.
Processing
drill hole
A drill hole is a narrow hole bored into the ground by a drilling machine, used to bring up samples of rock from deep underground so geologists can study what is there.
Technically: A drill hole is a borehole created by a drilling rig for the purpose of geological investigation, resource definition, geotechnical assessment, or hydrogeological testing; it is defined by its collar coordinates, azimuth, dip, and total depth, all of which must be surveyed to enable accurate three-dimensional plotting. In resource reporting, each drill hole is assigned a unique identifier, and its downhole survey data are used to reconstruct the actual path of the hole, which deviates from a straight line in most cases. Drill hole is the preferred term in technical reporting over the informal borehole when the context is mineral exploration, though the two are sometimes used interchangeably.
Geology
due diligence
Checking carefully where a material came from and whether anything harmful happened along the way before it reached you — like inspecting something thoroughly before you accept it.
Technically: A structured process by which a company identifies, assesses and addresses actual or potential risks in its mineral supply chain, including risks relating to conflict financing, human rights abuses, environmental violations and sanctions exposure. In the minerals context, due diligence frameworks — such as those published by the OECD — specify documentation, traceability and audit requirements at each stage of the chain from mine to market. Due diligence describes the process of investigation and risk management, and should not be treated as equivalent to certification, which is the outcome that third-party audit programmes may confer once due diligence has been satisfactorily completed.
Markets
electrolyte
A liquid, paste, or solid that lets electric charge travel through a battery or other device — like a highway for tiny charged particles moving between the two ends of a battery.
Technically: In electrochemical systems, an electrolyte is the medium that conducts ionic current between electrodes while remaining electrically insulating with respect to electron flow, thereby forcing electrons to pass through the external circuit. It may be a liquid solution of dissolved salts or acids, a polymer gel, a molten salt, or a solid ceramic, depending on the application and operating temperature. The electrolyte is often confused with the electrode: the distinction is that electrodes are the sites of oxidation and reduction reactions, whereas the electrolyte merely facilitates ion transport between them without itself being consumed in the principal cell reaction under normal operating conditions.
Materials
electrorefining
A way of purifying metal using electricity. An impure block of metal slowly dissolves in a liquid, and the pure metal re-forms on a clean sheet nearby, leaving the impurities behind.
Technically: Electrorefining passes a direct current through an electrolyte solution between an impure metal anode and a pure metal starting cathode, causing the anode to dissolve and the target metal to deposit selectively onto the cathode at a purity that can exceed the anode grade. Base metals more noble than copper remain undissolved, while less noble metals dissolve but do not deposit under the controlled voltage conditions, accumulating instead in solution or in the anode slime. The process is distinct from electrowinning, in which metal is deposited from a leach solution rather than from a dissolving metal anode.
Processing
enrichment
A process that increases the proportion of one particular variety of an element relative to the others — in uranium, that means increasing the share of the type of atom that can sustain a nuclear reaction.
Technically: Enrichment, in the context of nuclear materials, is the process of increasing the concentration of fissile uranium-235 relative to the more abundant uranium-238, most commonly by gaseous diffusion or gas centrifuge acting on uranium hexafluoride. Natural uranium contains a low proportion of U-235; most reactor designs require a higher proportion, and weapons-grade material requires a much higher proportion still. The term should not be confused with beneficiation or upgrading of metallic ores, where 'enrichment' is sometimes used loosely to mean increasing the grade of a concentrate; in nuclear fuel-cycle reporting, enrichment has a precise quantitative meaning expressed as assay in weight percent U-235.
Processing
evaporite
An evaporite is a rock made from minerals that were left behind when a body of salty water dried up, the way a ring of white salt forms around the edge of a puddle as it evaporates.
Technically: An evaporite is a sedimentary rock composed predominantly of minerals precipitated by the progressive concentration and eventual evaporation of saline water, either in marine basins or continental lake settings; common evaporite minerals include halite, gypsum, anhydrite, sylvite, and various borates and lithium salts. The sequence in which minerals precipitate follows solubility order, so the stratigraphic position within an evaporite succession indicates the degree of concentration the original brine reached and the depositional environment. Evaporites are economically significant both as ore themselves — potash and lithium brine deposits are evaporitic — and as host rocks or seals for other commodities, and their physical properties, particularly plasticity and low density, have important consequences for the structural geology of any basin in which they occur.
Geology
export control
A rule that says a country must give permission before certain materials or products can be sent abroad, like a gate that only opens with the right key.
Technically: A government-imposed restriction on the export of specified goods, technologies or materials, typically administered through licensing requirements. In minerals supply chains, export controls are applied to raw ores, concentrates or refined products that a producing country wishes to retain for domestic processing or to limit access by foreign parties. They are distinct from export taxes, which permit trade but impose a cost, whereas export controls can prohibit trade outright or subject it to case-by-case approval.
Markets
feasibility study
A detailed report that works out whether a mine can actually be built and make money, covering engineering, costs and environmental factors.
Technically: A feasibility study is a comprehensive technical and economic assessment of a mineral project at a level of detail sufficient to support a production decision and project financing. It applies modifying factors to resource estimates to produce reserve figures, and is expected to achieve a defined level of accuracy in capital and operating cost estimates. It sits above a pre-feasibility study in the hierarchy of studies and is distinguished from a preliminary economic assessment, which is permitted to include inferred resources and carries a lower standard of engineering rigour.
Markets
ferroalloy
An iron-based mixture that contains large amounts of another element — like manganese or chromium — and is added to steel during steelmaking to give the steel special properties.
Technically: A ferroalloy is a binary or more complex alloy of iron with one or more alloying elements — including manganese, silicon, chromium, nickel, molybdenum, vanadium, niobium, or others — produced in submerged-arc or electric-arc furnaces by smelting ore or oxide feeds in the presence of a reductant, typically coke. Ferroalloys are used almost exclusively as addition agents in steelmaking and cast-iron production, delivering the alloying element in a form that is easier to handle, store, and introduce to a melt than the pure metal alone. The distinction from master alloys is one of base metal and industry: ferroalloys are iron-based and directed at steel production, while master alloys are typically based on aluminium, copper, or nickel and used in non-ferrous foundry and casting operations.
Processing
flotation
A way of separating useful minerals from waste rock by mixing crushed ore with water and chemicals, then blowing in air bubbles. The mineral particles stick to the bubbles and float to the surface, while the waste sinks.
Technically: Froth flotation exploits differences in the surface chemistry of mineral particles: reagents called collectors make target mineral surfaces water-repellent, so air bubbles attach to them and carry them into a froth layer that overflows the cell, while hydrophilic gangue particles settle. The process is selective rather than universal—reagent choice and pH must be matched to the specific mineralogy—and the recovered froth product is called a concentrate. Flotation is sometimes confused with gravity separation, which instead exploits density differences and uses no reagents.
Processing
gangue
The useless rock mixed in with the valuable mineral. It has to be separated and discarded during processing.
Technically: Gangue comprises the minerals in an ore that have no commercial value in the context of the operation and must be separated from the target mineral during beneficiation. Its composition matters practically because certain gangue minerals — clays, talc, pyrrhotite — complicate flotation, leaching or smelting. The term is specific to the unwanted mineral fraction; the broader term for all displaced non-ore material is waste rock.
Geology
geophysics
Geophysics is the science of using physical measurements — such as gravity, magnetism, or electrical signals — to work out what kinds of rock or minerals lie underground without having to dig there first.
Technically: Applied geophysics in mineral exploration encompasses a range of techniques — including magnetics, gravity, seismic reflection, induced polarisation, electromagnetic, and radiometric surveys — that detect contrasts in physical rock properties such as density, magnetic susceptibility, electrical resistivity, and radioactive emission. Results are interpreted as anomalies relative to background, which then guide drill targeting rather than directly confirming the presence of ore. Geophysics is distinct from geochemistry, which measures elemental concentrations; the two disciplines are complementary and are routinely integrated in exploration programmes.
Geology
grade
How much of the valuable substance is in the rock, usually expressed as a small fraction — for example, grams of gold per tonne of rock, or a percentage of copper.
Technically: Grade is the concentration of a target commodity within a sample, block, or orebody, expressed in units appropriate to the commodity — mass percent for base metals, grams per tonne for gold and platinum-group elements, parts per million for trace elements, and carats per hundred tonnes for diamonds. Average grade must always be qualified by the volume or mass it represents, because a high-grade but small intersection and a low-grade but large one can carry identical contained metal. Grade as reported in a resource statement is a block-averaged figure, not a point measurement.
Geology
grain boundary diffusion
Atoms moving through a solid by travelling along the narrow gaps between the tiny crystal grains that make up a metal, which is much faster than moving through the grains themselves.
Technically: Grain boundary diffusion is the transport of atoms along the two-dimensional disordered zone between adjacent crystalline grains in a polycrystalline solid. Diffusion coefficients along grain boundaries are orders of magnitude higher than lattice diffusion coefficients within the bulk grain at the same temperature, so grain boundaries dominate mass transport at lower temperatures. In rare-earth magnet manufacturing, grain boundary diffusion treatment is used to introduce heavy rare-earth elements — typically dysprosium or terbium — into the surface regions of sintered neodymium-iron-boron magnets, improving coercivity while minimising the total quantity of heavy rare earth required.
Materials
greenfield
A greenfield project is an exploration effort in a place where no mining has ever taken place before, so the company is starting completely from scratch with no existing information about what lies underground.
Technically: A greenfield exploration project is one conducted in an area with no prior mining or significant modern exploration history, meaning there is no inherited infrastructure, no historical drill database, and no existing resource to guide targeting. Risk at the greenfield stage is highest because the geological model is largely unvalidated, but so is the potential for a discovery that has no historical discount applied to its scale. The term is routinely contrasted with brownfield, and in practice the boundary between the two is not always sharp: an area near a historical mine but geologically untested may be treated as greenfield for modelling purposes.
Geology
gross weight
The total weight of a shipment including the packaging, container or vehicle, not just the goods inside.
Technically: Gross weight is the combined mass of a consignment and all its packaging, dunnage or container, as opposed to net weight, which refers to the commodity alone, or dry metric tonne, which additionally excludes moisture. In bulk mineral trade the distinction between gross, net and dry-basis weights matters because payment is typically made on dry contained-metal tonnes, meaning that moisture content and packaging must be deducted before the commercially relevant quantity is established.
Materials
haul road
The wide ramp-like road inside or outside a mine that large trucks use to carry ore or waste rock from the pit or tunnel to the surface.
Technically: A purpose-built road within or adjacent to a mine workings, designed to carry heavy-duty haulage trucks — typically rigid-frame dump trucks of substantial capacity — between the working faces and the surface dump, stockpile, or processing plant. In open pit mines, haul roads spiral or switchback up the pit walls at a gradient constrained by the performance characteristics of loaded trucks. Road width, gradient, cross-fall, and surfacing are specified to suit vehicle size and traffic frequency. The haul road is a critical element of open pit geometry because its width and gradient directly affect the amount of waste rock that must be excavated to maintain access, influencing the strip ratio of the operation.
Mining
heap leaching
A process where crushed ore is piled into a large mound and a dissolving liquid is trickled through it; the liquid picks up the valuable metal and is then collected at the bottom for processing.
Technically: A hydrometallurgical process in which run-of-mine or crushed ore is stacked in a prepared heap on an impermeable liner, and a lixiviant — typically dilute sulfuric acid for copper or a cyanide solution for gold — is applied to the surface and allowed to percolate downward, leaching soluble target metals into solution. The pregnant leach solution draining from the base of the heap is collected and processed to recover the metal. Heap leaching is distinguished from tank or vat leaching by its use of large unstirrred outdoor piles, which makes it suited to low-grade ores where the capital cost of finer grinding and agitated leaching would not be recovered; extraction efficiency is generally lower than with more intensive leaching methods.
Mining
heavy rare earth
The rare earth metals from the heavier end of the group — such as dysprosium, terbium and yttrium — which are rarer and harder to find in large deposits.
Technically: Heavy rare earth elements (HREEs) are conventionally taken as gadolinium through lutetium, plus yttrium, distinguished by higher atomic numbers, greater ionic charge density and relative scarcity in most commercial ore bodies. They are enriched in ion-adsorption clay deposits and in monazite. HREEs tend to command higher prices than LREEs because workable concentrations are rarer and fewer deposits are in production; their supply is therefore considered more constrained. The same boundary ambiguity that affects the LREE definition applies here.
Materials
high-purity quartz
Sand or rock made almost entirely of the mineral quartz, with barely any other substances mixed in — so clean that it can be used to make the glass inside computer chips and solar panels.
Technically: High-purity quartz refers to silicon dioxide (SiO₂) material in which the total concentration of impurity elements — including aluminium, titanium, iron, and alkali metals — has been reduced to the parts-per-million or parts-per-billion range through beneficiation and thermal or chemical purification. In practice it is distinguished from ordinary silica sand or quartz grit by its suitability for crucible and semiconductor-grade applications, where even trace impurities compromise crystal growth or optical transmission. The term is sometimes used loosely to include any washed silica, but technically it implies verified chemical analysis meeting the thresholds specified by downstream processors.
Materials
host rock
The body of ordinary rock that surrounds or contains a mineral deposit — the background rock that the ore or veins sit inside.
Technically: Host rock is the pre-existing rock body within which mineralisation has been emplaced, precipitated, or formed, irrespective of whether that rock was chemically altered in the process. The term is descriptive and spatial rather than genetic: it identifies what the deposit is hosted in without implying a particular origin for the mineralisation. In metasomatic systems such as skarns, the host rock is substantially modified, while in many vein systems it may be largely unchanged; both usages are correct, and care is needed not to conflate 'host rock' with 'unaltered country rock'.
Geology
hydrometallurgy
Extracting metals by dissolving the ore in liquid and then recovering the metal from that liquid, rather than by melting anything.
Technically: Hydrometallurgy encompasses the aqueous processing routes used to extract, separate and recover metals, typically operating at or near ambient temperature and pressure — though pressure leaching is a significant exception. The three principal unit operations are leaching (dissolution of the metal into solution), solution purification and concentration (e.g. solvent extraction, ion exchange), and metal recovery (e.g. electrowinning, precipitation, cementation). It is distinguished from pyrometallurgy by the working medium — water-based solutions rather than high-temperature melts or gases — and the two are frequently combined in sequence within a single flowsheet.
Processing
hydrothermal
Anything to do with hot water moving through cracks in the Earth's crust, often carrying dissolved metals that crystallise out when the water cools.
Technically: In economic geology, 'hydrothermal' describes processes, fluids, and deposits formed by the circulation of heated aqueous solutions through fractures and permeable zones in the crust. These fluids may derive from magmatic, metamorphic, or meteoric sources, and deposit minerals as temperature, pressure, or chemistry changes along the flow path. The term covers a wide range of deposit styles — from high-temperature porphyry systems to low-temperature epithermal veins — so it should always be qualified by temperature regime or deposit type in technical usage.
Geology
in-situ recovery
A way of extracting minerals by pumping liquid down into the ore deposit, dissolving the useful minerals underground, and then pumping the liquid back up to the surface — no digging required.
Technically: A method in which a lixiviant — a dissolving solution, most commonly an acid or alkaline solution — is injected into an orebody through boreholes, allowed to react with and dissolve the target minerals within the deposit, and then recovered through separate extraction boreholes as a pregnant solution for processing at surface. The method is most widely applied to sandstone-hosted uranium deposits and some copper deposits. It is often called in-situ leaching (ISL), and the terms are used interchangeably in practice; the key practical distinction from heap leaching is that in-situ recovery does not involve any mining or movement of rock.
Mining
indicated resource
A part of a deposit that geologists have a reasonable but not complete picture of, based on samples that are spread a bit further apart.
Technically: An indicated resource is one for which quantity, grade or quality, densities, shape and physical characteristics can be estimated with sufficient confidence to allow a mine plan to be applied and for assumptions about technical and economic parameters to be made. Sample spacing is wider than for a measured resource, and geological continuity is assumed but not fully demonstrated. An indicated resource can support a pre-feasibility study and may convert to a probable reserve; it cannot directly support a proven reserve.
Markets
industrial mineral
A mineral or rock dug up not for the metal inside it but for its own physical or chemical properties — things like salt, gravel, potash or kaolin used directly in factories or construction.
Technically: An industrial mineral is any non-metallic, non-fuel mineral or rock exploited for its inherent physical or chemical properties rather than as a source of extractable metal. Examples include potash, phosphate rock, kaolin, barite, silica sand and talc. The category is defined by end use and contrasts with both metallic ores and energy minerals; the same material, such as graphite, may appear on both industrial-mineral and critical-mineral lists depending on the analytical framework applied.
Materials
inferred resource
A rough estimate of ore that might be in the ground, based on limited information and a lot of geological guesswork.
Technically: An inferred resource is one for which quantity and grade or quality are estimated on the basis of limited geological evidence and sampling, sufficient only to imply but not verify geological and grade continuity. The level of confidence is too low to apply many technical or economic parameters with reliability. Inferred resources cannot be converted directly to reserves and are excluded from economic analysis in feasibility studies; they are sometimes included in scoping or preliminary economic assessments with explicit caveats.
Markets
ion-adsorption clay
An ion-adsorption clay is a type of weathered rock in which rare earth elements are not locked tightly inside mineral crystals but instead cling loosely to the surface of clay particles, a bit like static-charged dust sticking to a screen, making them relatively easy to recover.
Technically: Ion-adsorption clay deposits, also called in-situ leach rare earth deposits or weathered crust elution-deposited rare earth deposits, form by deep tropical or subtropical weathering of granitic or volcanic parent rocks, during which rare earth elements are released from primary minerals and adsorbed onto the surface of secondary clay minerals — principally halloysite, kaolinite, and smectite — rather than forming discrete rare earth minerals. Because the elements are electrostatically bound rather than structurally incorporated, they can be displaced into solution by treatment with ammonium sulfate or other electrolyte solutions at relatively low temperatures, which gives these deposits a processing advantage over hard-rock rare earth ores despite their typically low total rare earth oxide grades. They are the principal global source of heavy rare earth elements, which are preferentially enriched in them relative to the light rare earth elements that dominate most hard-rock deposits such as carbonatites.
Geology
kimberlite
A rare type of rock that erupts violently from very deep in the Earth and sometimes brings diamonds with it, forming carrot-shaped pipes in the crust.
Technically: Kimberlite is a volatile-rich, ultramafic to potassic igneous rock emplaced from depths in excess of roughly 150 km, typically forming sub-vertical, roughly cylindrical bodies called pipes, dykes, and sills. It is the principal primary host for diamond, carrying xenoliths of mantle material including diamond-bearing peridotite. Kimberlite is often confused with lamproite, which can also be diamond-bearing; the distinction matters in exploration because the two rock types have different indicator-mineral suites and eruption styles.
Geology
laterite
A layer of deeply weathered soil or rock found in tropical regions, where heavy rainfall over millions of years has dissolved away most minerals and left iron and aluminium compounds behind. Some laterites are mined for nickel or bauxite.
Technically: Laterite is a residual weathering product formed by intense and prolonged tropical or subtropical weathering that leaches silica and soluble cations from parent rock, leaving a material enriched in iron oxides, aluminium oxyhydroxides, and sometimes nickel, cobalt, or manganese. The term encompasses a spectrum from soft, clayey saprolite at depth to a hard, indurated ferruginous crust or duricrust at the surface. In the mining context, lateritic nickel deposits are distinct from magmatic sulfide nickel deposits in both mineralogy and processing requirements: the nickel is hosted in oxide and silicate minerals rather than sulfides, making pyrometallurgical and hydrometallurgical treatment substantially different.
Geology
leaching
Dissolving the useful metal out of ore or crushed rock using a liquid, usually an acid or an alkaline solution. The metal passes into the liquid and can then be collected from it.
Technically: Leaching is a hydrometallurgical operation in which a lixiviant—most commonly sulfuric acid for copper oxide ores, cyanide solution for gold, or caustic soda for bauxite—is brought into contact with crushed or run-of-mine ore to dissolve the target metal selectively into solution. The resulting pregnant leach solution is then processed by solvent extraction, ion exchange, or direct electrowinning to recover the metal. Leaching is the first step in a hydrometallurgical route and is used where ore mineralogy or grade makes pyrometallurgical processing uneconomic; it is operationally distinct from smelting, which requires heat rather than chemical solvation.
Processing
light rare earth
The rare earth metals from the lighter end of the group — lanthanum, cerium and their near neighbours — which tend to be more abundant and cheaper than the heavier ones.
Technically: Light rare earth elements (LREEs) are conventionally taken as lanthanum through europium (or sometimes through gadolinium), characterised by lower atomic numbers and higher relative abundance in most deposits. They are enriched in carbonate-hosted deposits such as bastnäsite ores. The exact boundary with heavy rare earths is not universally agreed: some classifications place neodymium and samarium in the light group, others split them differently, so the division should be checked against a specific source when precision is required.
Materials
longwall
A way of mining underground where a long cutting machine shears back and forth across a wide face of ore or coal, and the roof behind it is allowed to collapse in a controlled way as the machine moves forward.
Technically: An underground extraction method in which a powered shearer traverses a long working face — the longwall — while hydraulic shields support the immediate roof above workers and equipment; as the face advances, the roof behind the shields is allowed to cave in a controlled manner into the mined-out void, known as the goaf. Longwall is predominantly used for flat-lying coal seams but is also applied to certain potash and salt deposits. It achieves high extraction ratios and high production rates but requires consistent seam geometry and is not readily applied to irregular or steeply dipping orebodies, which distinguishes it from room-and-pillar workings.
Mining
master alloy
A ready-made mixture of metals with a higher concentration of an additive than you want in the final product, so that a metalworker can stir in a small, precise amount and get exactly the right composition.
Technically: A master alloy is a pre-alloyed intermediate, usually based on aluminium, copper, or nickel, that contains a high concentration of one or more alloying or grain-refining elements and is formulated to dissolve readily when added in controlled quantities to a larger melt. The dilution approach allows precise compositional adjustment without the difficulty of handling small quantities of reactive or refractory pure metals directly. Master alloys are distinguished from ferroalloys by their non-ferrous base and by the relatively small addition rates typically involved; they are also distinct from hardeners in some industry usages, though the terms overlap in non-ferrous foundry practice.
Processing
material intensity
How much of a particular material is needed to make one unit of something — for example, how many kilograms of copper go into one electric car.
Technically: The quantity of a given material consumed per unit of output, product or economic activity, typically expressed in mass per unit (tonnes per megawatt of generating capacity, grams per vehicle and similar measures). Material intensity is used to link demand forecasts for end products to derived demand for the underlying mineral. It is distinct from material efficiency, which describes how much of the input material is successfully incorporated into the final product rather than lost as process waste; high material intensity and low material efficiency can coexist in the same production system.
Markets
matte
A thick, heavy liquid produced partway through smelting sulfide ores, made mostly of metal sulfides mixed together. It still needs further treatment before pure metal can be extracted from it.
Technically: Matte is an intermediate pyrometallurgical product consisting predominantly of metal sulfides—in copper production, mainly copper sulfide and iron sulfide—formed when a sulfide concentrate is smelted under controlled oxidising conditions. Its grade is expressed as the percentage of copper (or nickel, in nickel smelting) it contains, and raising this grade is the objective of the converting step that follows. Matte is distinct from slag, which is the silicate-dominated waste layer that separates above or below it in the furnace depending on density relationships.
Processing
measured resource
The part of a deposit that geologists know about in the greatest detail, based on closely spaced samples and tests.
Technically: A measured resource is one for which quantity, grade or quality, densities, shape and physical characteristics are estimated with a high level of confidence, derived from closely spaced sampling and detailed geological interpretation. It is the highest-confidence category within the resource classification and is the only category that can convert to a proven reserve once economic and technical criteria are met. It is sometimes confused with a proven reserve, but until a feasibility study confirms economic viability the material remains a resource, not a reserve.
Markets
mill
A mill is the building or whole site where ore is crushed, ground, and processed after it leaves the mine. The word also names the individual machine that grinds rock into fine powder.
Technically: In mining, 'mill' is used at two scales that must be distinguished by context. At the equipment level it refers to a grinding machine—most commonly a ball mill, rod mill, SAG mill, or AG mill—that reduces crushed ore to the fine particle sizes required for mineral liberation. At the facility level, 'mill' or 'mill complex' denotes the entire processing plant that receives run-of-mine or crushed ore and produces a saleable concentrate or other upgraded product. Confusion arises when 'mill' and 'concentrator' are used interchangeably for the facility; strictly, a mill may include unit operations beyond concentration, such as filtration and tailings management, whereas a concentrator is defined by its separation function.
Mining
mine life
Mine life is the number of years a mine is expected to keep producing, based on how much ore has been identified and how fast it will be mined. When the ore runs out, the mine closes.
Technically: Mine life is the projected operating period of a mine from commencement of production to exhaustion of the economically recoverable reserve, calculated by dividing the total proven and probable ore reserve by the planned annual throughput rate. It is a forward-looking estimate and changes as new reserves are delineated, as throughput rates are revised, or as the cut-off grade is adjusted in response to commodity prices. Mine life should not be confused with the life of the mineral resource, which is a larger and less certain quantity; the reserve is the subset underpinning the life calculation.
Mining
mineralisation
The presence of useful or interesting minerals concentrated in rock, not necessarily enough to mine but enough to be worth studying.
Technically: Mineralisation is the occurrence of one or more minerals of economic or potential economic interest within a rock body, introduced or concentrated by geological processes. The term is intentionally non-committal about grade or quantity, and its use in technical reporting deliberately avoids the implication that the material qualifies as a mineral resource under any reporting code. It is often used in early exploration to describe anomalous concentrations before sufficient data exist to classify the occurrence formally; once adequate drilling and sampling have been completed, the material may be reclassified as a mineral resource or found to fall below economic thresholds.
Geology
net import reliance
A measure of how much of a country's supply of a material has to come from other countries because it does not produce enough at home to meet its own needs.
Technically: Net import reliance (NIR) expresses a country's dependence on foreign sources for a commodity as imports minus exports, adjusted for changes in government and industry stock levels, divided by apparent consumption — typically reported as a percentage. A positive NIR indicates net import dependence; a value at or near the full percentage indicates the country produces virtually none domestically. The measure is used in supply-risk assessments to identify materials where a disruption to international trade flows would constrain domestic consumption. It is a structural indicator and does not distinguish between supply from allied and non-allied trading partners, which limits its use as a standalone risk metric.
Markets
offtake agreement
A long-term promise by a buyer to purchase a set amount of a material from a mine or plant, often signed before the mine is even built, to give the producer confidence it will have a customer.
Technically: An offtake agreement is a commercial contract in which a buyer commits to purchase a defined volume or share of a project's output over a specified period, typically at a price linked to a market reference at the time of delivery rather than fixed in advance. Such agreements are commonly used to underpin project financing, since the guaranteed revenue stream reduces lender risk. Key variables include the volume commitment (which may be a floor, a ceiling or a percentage of production), the pricing formula, the treatment and refining charges deducted for concentrates, and the conditions under which either party may terminate or renegotiate.
Markets
open pit
A mine that works in the open air by digging a giant bowl-shaped hole in the ground, removing rock layer by layer from the top down.
Technically: A surface mining method in which mineralised rock is extracted from an open excavation, typically stepped into a series of descending benches, without any underground workings. The method is chosen when the orebody is broad, relatively shallow, and the strip ratio — the volume of waste rock that must be moved per unit of ore — remains economically acceptable at the planned depth. It is sometimes called open-cut or open-cast mining, though open-cast more precisely refers to the excavation of shallow, flat-lying deposits where the original surface is later restored.
Mining
opex
The money a mine or factory spends to keep running day to day — wages, fuel, chemicals and so on — as opposed to the big one-off costs of building it in the first place.
Technically: Operating expenditure covers all costs incurred in the ongoing production process: labour, energy, reagents, maintenance consumables and site-level administration. It is distinguished from capital expenditure (capex), which funds assets with a working life extending beyond the accounting period. In mine-cost analysis, opex is often expressed per unit of output — per tonne milled or per pound of metal produced — making it the primary basis for comparing operational efficiency across sites.
Markets
ore
Rock that contains enough of a useful mineral to be worth digging up and processing. Rock with the same mineral but too little of it is just rock.
Technically: Ore is rock or sediment from which one or more commodities can be extracted at a profit under the prevailing economic and technical conditions. The classification is economic, not purely geological: the same material can be ore at one metal price and waste at another. It is often confused with 'mineral', which refers to a specific chemical compound regardless of whether its occurrence is economically exploitable.
Geology
orebody
A distinct mass of ore in the ground with a recognisable shape — like a thick underground blob or sheet of valuable rock that has been mapped out.
Technically: An orebody is a continuous, three-dimensionally defined volume of rock that meets the criteria for ore and is sufficiently coherent in geometry and grade to be treated as a discrete extraction target. The term implies that the boundaries have been established by drilling or sampling, distinguishing it from a mere mineralised occurrence or prospect. A single deposit may contain several separate orebodies if high-grade zones are separated by material that does not meet cut-off grade.
Geology
outcrop
A place where solid bedrock is exposed at the surface, not covered by soil, loose sediment, or vegetation — the rock you can walk up to and touch.
Technically: An outcrop is any exposure of in-situ bedrock or mineralisation at the Earth's surface, whether natural (erosion, cliff face, stream cut) or artificial (road cut, quarry face). In field mapping and early-stage exploration, outcrop is significant because it allows direct sampling and observation without drilling or trenching. The extent of outcrop should not be equated with the extent of the underlying unit, since the same rock body may extend considerable distances beneath cover; conversely, an apparently continuous outcrop may be interrupted by faulting that is invisible from the surface.
Geology
overburden
All the soil, loose rock, and waste material sitting on top of a mineral deposit that has to be moved out of the way before mining can begin.
Technically: Overburden refers to the mass of rock, regolith, and soil overlying an orebody or target stratum that must be stripped or excavated to gain access to the material of interest, particularly in surface mining. The ratio of overburden volume to ore volume (the strip ratio) is a primary determinant of the economics of open-pit and strip mining. In some technical contexts, particularly in sedimentary basin studies, the term is used more broadly to denote any overlying rock sequence regardless of mining context, which can cause ambiguity; the intended meaning should be clear from context.
Geology
oxide equivalent
A way of describing how much of a metal is present by pretending it has all been turned into its oxide form, even if it is actually in the ground as a different compound.
Technically: Oxide equivalent is a reporting convention in which the quantity of a metal or suite of metals is expressed as the mass of the corresponding oxide or oxides that would be formed if all the metal were fully oxidised. It is standard in rare-earth reporting, where individual elements are reported as their trioxides (e.g. La₂O₃, CeO₂) and totals are summed as total rare earth oxide. Because oxide equivalent inflates mass relative to contained metal by a factor that varies by element, it cannot be compared directly with contained-metal figures without applying the appropriate elemental conversion factor.
Materials
pegmatite
An igneous rock with exceptionally large crystals — sometimes as long as your arm. Pegmatites often contain unusual elements like lithium, caesium, and rare-earth metals that got concentrated into the last fluids as a magma cooled.
Technically: Pegmatite is an intrusive igneous rock characterised by an extremely coarse crystal size, conventionally with a median grain size exceeding a few centimetres, formed from volatile-enriched residual melts or fluxed crystallisation in the final stages of magmatic cooling. The high concentrations of water, fluorine, boron, and lithium in these residual melts allow rare and large-ion-lithophile elements — lithium, caesium, rubidium, beryllium, tantalum, niobium, tin, and rare earths — to reach exploitable concentrations. Lithium-caesium-tantalum (LCT) pegmatites are the principal hard-rock source of lithium globally and are distinguished from the niobium-yttrium-fluorine (NYF) family by their geochemical affinity and tectonic setting.
Geology
placer deposit
A natural concentration of heavy or tough minerals that have been washed out of older rocks and settled in a riverbed, beach, or ancient valley floor, much like gold settling to the bottom of a prospector's pan.
Technically: A placer deposit forms when weathering liberates resistant, dense minerals from their source rocks and flowing water, wind, or wave action sorts and concentrates them by specific gravity. Economically significant placers include alluvial (river), eluvial (hillslope), and marine shoreline varieties. The term is sometimes loosely applied to aeolian concentrations, but strictly these require separate qualification because the sorting mechanism differs from hydraulic settling.
Geology
platinum-group metal
A family of six rare silvery metals — including platinum, palladium and rhodium — that share similar properties and are often found together in the same rocks.
Technically: The platinum-group metals (PGMs) are platinum, palladium, rhodium, ruthenium, iridium and osmium, grouped together on the basis of shared geochemical behaviour, mutual occurrence in the same sulphide ore bodies, and broadly similar physical and catalytic properties. They are extracted principally as co-products or by-products of nickel and copper sulphide mining. Because PGMs partition differently within an ore and into different refinery streams, their individual supply ratios are largely fixed by geology and cannot be adjusted independently of one another.
Materials
polysilicon
Extremely pure silicon made by refining ordinary silicon through chemical processes until it is clean enough to be used in solar panels and computer chips.
Technically: Polysilicon, or polycrystalline silicon, is silicon refined to a purity that removes nearly all metallic and non-metallic impurities, typically through conversion of metallurgical-grade silicon to a gaseous intermediate such as trichlorosilane, followed by chemical vapour deposition. The resulting material is polycrystalline in structure and serves as the feedstock for both the Czochralski process, which produces monocrystalline silicon wafers for semiconductors and high-efficiency solar cells, and for direct casting of multicrystalline ingots used in standard photovoltaic modules. Polysilicon should not be confused with metallurgical-grade silicon, from which it is derived but which is of substantially lower purity and commands a different price.
Materials
porphyry
A type of igneous rock that has large crystals scattered through a finer-grained background, like chocolate chips in a biscuit. Several of the world's biggest copper and gold mines are found in porphyry rock.
Technically: In economic geology, porphyry refers both to the igneous rock texture — phenocrysts set in an aphanitic or fine-grained groundmass — and to a class of large, low-grade, disseminated metal deposits genetically linked to shallow intrusions of porphyritic composition. Porphyry copper deposits, which may also carry molybdenum, gold, or silver, are typically of low grade but very large tonnage, with mineralisation distributed through a network of stockwork veins and fractures rather than in discrete high-grade shoots. They are distinguished from skarn and epithermal deposits by their intrusion-centred, stockwork-controlled geometry and broadly calc-alkaline host magmatism.
Geology
precious metal
Metals like gold, silver and platinum that are rare, do not corrode easily and have historically been used as money or jewellery as well as in industry.
Technically: Precious metals are those with high economic value per unit mass, arising from a combination of relative scarcity, chemical resistance to corrosion, and sustained demand for monetary, ornamental and industrial uses. Gold, silver and the platinum-group metals are the standard members of this category. The distinction from base metals is partly chemical — precious metals are nobler and more resistant to oxidation — but is equally a market convention reflected in separate trading, pricing and custody arrangements.
Materials
precursor
A material that has been prepared partway through a process and is ready to be turned into the final product — like a cake mix that still needs baking.
Technically: In materials processing, a precursor is an intermediate compound manufactured to a controlled specification and intended as the direct feed for a subsequent reaction that yields the end product. In lithium-ion battery supply chains the term most commonly refers to precursor cathode active material (PCAM) — typically a co-precipitated mixed hydroxide of nickel, manganese, and cobalt — which is blended with a lithium source and calcined to produce cathode active material. Confusion arises because 'precursor' is used across many industries with slightly different scopes; the battery-industry sense is narrower and more chemically specific than the general industrial usage.
Processing
probable reserve
Ore that experts are fairly sure can be mined at a profit, though with a little less certainty than a proven reserve.
Technically: A probable reserve is derived from at least an indicated resource, with modifying factors applied and economic viability demonstrated through a pre-feasibility or feasibility study, but with somewhat less geological or technical certainty than a proven reserve. In practice, probable reserves often constitute the majority of a mine's declared reserves. The distinction from proven reserves matters in financing and reporting contexts, where lenders or regulators may weight the two categories differently.
Markets
prospect
A prospect is a place where geologists have found enough signs of valuable minerals to investigate further, but where no one yet knows whether there is enough to mine.
Technically: A prospect is an area of mineralisation interest that has been identified by surface sampling, mapping, or geophysical surveys and has received some exploratory attention, but which has not yet been sufficiently drilled or tested to support a mineral resource estimate under any recognised reporting code. It sits between a raw anomaly, which is merely a measurement departure, and a deposit, which has defined mineralisation geometry and grade continuity. The term carries no implication of economic viability; conflating prospect with deposit or resource is a common and consequential error in non-technical communication.
Geology
proven reserve
The most certain kind of minable ore: engineers have checked it very carefully and are confident it can be dug up and sold at a profit.
Technically: A proven reserve is the highest-confidence category of mineral reserve, derived from a measured resource after the application of modifying factors—including mining, metallurgical, economic, marketing, legal, environmental, social and governmental considerations—demonstrated through a feasibility study. Because it requires both high geological confidence and demonstrated economic viability, the proven category is typically smaller in tonnage than probable or inferred categories. It is the figure most directly relevant to mine life and financing decisions.
Markets
pyrometallurgy
Extracting or refining metals using very high heat — think of a furnace hot enough to melt rock — to separate the metal from everything else.
Technically: Pyrometallurgy covers the high-temperature processing operations — including smelting, roasting, calcination, sintering and converting — used to extract metals from ores or concentrates and to refine crude metal. Reactions occur in solid, liquid or gas phases at temperatures typically ranging from a few hundred to well over a thousand degrees Celsius. The approach contrasts with hydrometallurgy in that separation relies on differences in melting points, oxidation potentials and slag–matte–metal phase equilibria rather than on aqueous chemistry; in practice many industrial flowsheets use pyrometallurgical and hydrometallurgical stages in series.
Processing
rare earth element
A group of seventeen metals that share similar chemical behaviour and are used in small but important quantities in magnets, screens and many other technologies.
Technically: The rare earth elements comprise the fifteen lanthanides (lanthanum through lutetium, atomic numbers 57–71) together with scandium and yttrium, which are grouped with them because of geochemical and chemical similarities. Despite the name, most are not especially scarce in Earth's crust; they are called rare partly for historical reasons and partly because concentrated, economically workable deposits are less common than crustal abundance alone would suggest. They are routinely divided into light and heavy subgroups, though the boundary used varies between sources.
Materials
recovery rate
Recovery rate is the share of a valuable mineral that is actually captured during processing, expressed as a proportion of the amount that was in the ore to begin with. If a lot of gold goes out with the waste, the recovery rate is low.
Technically: Recovery rate, in mineral processing, is the proportion of the target element or mineral in the feed that is successfully extracted and reported to the product stream, typically expressed as a percentage. It is calculated from the assay grades and masses of the feed, concentrate and tailings streams and represents the efficiency of the processing circuit. Recovery rate must be distinguished from grade: a process achieving a high recovery may still produce a low-grade concentrate, and optimising one often involves trade-offs with the other. Metallurgical recovery is a key variable in the calculation of payable metal and in the economic evaluation of an orebody.
Mining
refractory metal
A metal that stays solid and strong even at temperatures hot enough to melt most other metals. Tungsten, molybdenum, niobium, tantalum and rhenium are the main ones.
Technically: Refractory metals are conventionally defined as those with melting points above approximately that of platinum, a group that in practice centres on tungsten, molybdenum, tantalum, niobium and rhenium. Their defining practical characteristic is retention of mechanical strength at elevated service temperatures where steels and most non-ferrous alloys would creep or fail. The term is sometimes extended loosely to chromium or vanadium, but in technical literature it is most reliably applied to the five metals listed above.
Materials
reserves
The part of a mineral deposit that a mining company has confirmed it can dig up and sell at a profit, given today's technology and prices.
Technically: Reserves are that portion of a mineral resource for which sufficient study has been completed to demonstrate that extraction is technically feasible and economically viable under stated assumptions. The category sits beneath resources in the classification hierarchy and requires a completed feasibility or pre-feasibility study to support it; a resource does not become a reserve simply by being well-drilled.
Markets
resource nationalism
When a country's government decides it wants more control or a bigger share of the profits from the minerals found within its borders, sometimes taking over mines or changing the rules that foreign companies operate under.
Technically: Resource nationalism describes a range of government actions through which a state asserts greater control over mineral resources or appropriates a larger share of the economic rents from their extraction. Measures include increased royalty or tax rates, mandatory local ownership or processing requirements, export restrictions on unprocessed ore, renegotiation or cancellation of existing concession agreements, and full or partial nationalisation. The term covers a spectrum of interventions rather than a single policy type, and its application to any specific government action often reflects the perspective of the party describing it. In supply-chain analysis it is treated as a category of political risk that can affect the availability and cost of supply from a given jurisdiction.
Markets
resources
A mineral deposit that geologists have found and measured, but where no one has yet proved it can be mined at a profit.
Technically: A mineral resource is a concentration of material of potential economic interest in or on the Earth's crust, in a form and quantity that there are reasonable prospects for eventual economic extraction. Resources are classified by the confidence of the geological estimate into measured, indicated and inferred categories. They are routinely confused with reserves, but the distinction is consequential: resources carry no guarantee of economic extractability, whereas reserves do.
Markets
roasting
Heating ore in air at high temperature to cause a chemical reaction — most often turning sulfur compounds into gases and leaving behind a solid that is easier to process.
Technically: Roasting is a pyrometallurgical operation in which finely divided ore or concentrate is heated in a controlled atmosphere, most commonly air or oxygen, to achieve a specific chemical transformation of the solid feed — classically the oxidation of metal sulfides to oxides and sulfur dioxide. Unlike calcination, roasting is defined by the intentional reaction between the solid and the furnace atmosphere rather than simple decomposition. Several variants exist: oxidising, sulfating, magnetising and chloridising roast each target a different product phase, and the distinction between them is operationally significant when selecting downstream leach or smelting conditions.
Processing
room and pillar
An underground mining method where miners dig out sections of ore and leave behind regular columns of unmined rock, like pillars holding up the ceiling of a room.
Technically: A method of underground mining in which ore is extracted from a grid of openings — the rooms — while regular columns of intact ore or rock — the pillars — are left in place to support the overlying strata. The method suits flat-lying or gently dipping, competent orebodies of moderate thickness, such as coal seams, potash beds, or tabular mineral deposits. It is sometimes confused with stope-and-pillar mining; the distinction is that room and pillar implies a systematic, near-regular pillar pattern designed from the outset, whereas stope-and-pillar arrangements may be more irregular and adapted to ore geometry.
Mining
royalty
A payment — usually a share of the value of what is mined — made to whoever owns the ground or holds a financial interest, every time metal is produced and sold.
Technically: A mineral royalty is a periodic payment made to a rights holder — which may be a government, a landowner or a royalty finance company — calculated as a percentage of revenue, profit, or output value. Common structures include the net smelter return (NSR) royalty, which applies to the value of metal received at the smelter after deducting treatment and refining charges, and the gross overriding royalty, which applies to gross revenue before such deductions. Royalties differ from streaming agreements in that the royalty holder receives cash rather than metal, and differs from a working interest in that the royalty holder bears none of the operating costs. Governments typically impose statutory royalties separately from, and in addition to, any contractual royalties.
Markets
run of mine
Run of mine is the rock that comes straight out of the mine before anything has been sorted, crushed or processed. It is a mixture of valuable ore and worthless rock, just as it was blasted out of the ground.
Technically: Run of mine (ROM) material is the total broken rock delivered from the mining face to the primary crusher or stockpile without any prior sorting or beneficiation. Its grade reflects the combined effect of the in-situ ore grade and the dilution introduced by mining, making ROM grade typically lower than the sampled resource grade. ROM grade and tonnage are the primary inputs to mill feed planning, and the gap between the sampled resource grade and the ROM grade as-received is a common measure of operational dilution performance.
Mining
salar
A vast, flat salt flat found in the high deserts of South America. Beneath the salt crust lies salty water — called brine — which in some salars contains lithium at concentrations high enough to be mined.
Technically: A salar is an endorheic salt flat occupying a closed basin in an arid to hyper-arid environment, characterised by an evaporite surface crust — predominantly halite, with variable sulfates and carbonates — and a subsurface porous horizon saturated with concentrated brine. The term is used most precisely for the high-altitude basins of the central Andean Puna plateau, though analogous features occur elsewhere. In the lithium industry, salars are significant because the brines beneath the crust of certain basins carry elevated lithium concentrations derived from volcanic inputs and long-term evaporative concentration; the geometry and hydrogeology of the brine aquifer govern the economics of extraction.
Geology
scrap ratio
The share of total metal supply that comes from recycled scrap rather than freshly mined and refined metal — the higher it is, the more a market relies on old metal.
Technically: The proportion of total metal supply, or of input to a smelting or refining process, that is derived from scrap rather than from primary concentrates or refined primary metal. The ratio can be calculated at the level of an individual facility, a country or a global market, and the denominator and numerator must be clearly specified to allow meaningful comparison. A high scrap ratio reduces primary ore requirements for a given output level but does not eliminate them, since scrap availability is bounded by the accumulated in-use stock of the metal and the collection efficiency of end-of-life systems.
Markets
secondary supply
Metal or mineral material that comes from recycling old products rather than from digging new ore out of the ground.
Technically: The portion of total material supply derived from the recovery and processing of end-of-life products, manufacturing scrap or process residues, as distinct from primary supply sourced from mined ore. Secondary supply is subdivided into old scrap, generated by post-consumer products reaching end of life, and new scrap, arising within manufacturing processes. The distinction from primary supply matters for environmental accounting, for assessing supply security (since secondary supply is less geographically concentrated than primary mining) and for understanding price dynamics, as secondary supply responds differently to price signals than mining output does.
Markets
separator
A very thin, porous sheet placed between the two sides of a battery to stop them touching and short-circuiting, while still letting the charged particles pass through its tiny holes.
Technically: A separator is a permeable membrane positioned between the anode and cathode of an electrochemical cell to prevent direct electronic contact — and the short-circuit current that would result — while allowing ions to migrate through its pores via the electrolyte. In lithium-ion cells, separators are typically microporous polymer films, though ceramic-coated variants are also used to improve thermal stability. The separator is sometimes conflated with the electrolyte because both occupy the space between electrodes, but the separator is a distinct structural component: it provides mechanical separation and does not itself conduct ions; ion transport occurs through the electrolyte held within or alongside it.
Materials
shaft
A vertical tunnel sunk straight down into the ground from the surface, used to carry miners, equipment, and ore up and down in an underground mine.
Technically: A vertical or near-vertical excavation connecting the surface to one or more levels of an underground mine, used for the hoisting of personnel, materials, and ore or waste rock, and for ventilation. Shafts are sunk by drilling and blasting or by mechanical shaft-boring, and are lined with concrete or steel sets to maintain stability. A production shaft is distinguished from a ventilation shaft by its primary function and by the presence of hoisting infrastructure — headframe, winding engine, and conveyances — though a single shaft may serve multiple purposes. Shafts are preferred over declines for deep, high-tonnage operations because hoisting is faster than trucking over long vertical distances.
Mining
single crystal
A piece of metal or other solid that has been grown so that all its atoms line up in one continuous, uninterrupted pattern from edge to edge, with no joins or boundaries inside.
Technically: In materials science a single crystal is a solid in which the crystalline lattice is continuous and uninterrupted throughout the entire volume of the component, with no grain boundaries present. In the context of superalloy turbine blades, single-crystal casting eliminates the grain boundaries that are the preferred sites for high-temperature creep and oxidation, substantially extending blade life. The term is often contrasted with directionally solidified and equiaxed castings, which represent intermediate and conventional conditions respectively; the distinction matters because each requires a different casting process and commands a different performance specification.
Materials
sintered magnet
A strong permanent magnet made by pressing metal powder into a mould and baking it at high heat until the particles fuse together, like pressing damp sand into a brick and letting it dry hard.
Technically: A sintered magnet is produced by milling an alloy — most commonly neodymium-iron-boron or samarium-cobalt — to a fine powder, aligning the particles in a magnetic field, pressing them into a green compact, and then sintering at elevated temperature to bond the particles without fully melting them. This route produces the highest magnetic energy products achievable in commercial permanent magnets. Sintered magnets are distinguished from bonded magnets, in which the same alloy powders are held in a polymer matrix; bonded magnets have lower magnetic performance but can be formed into complex near-net shapes.
Materials
sintering
Heating small particles of material until they just start to stick together and fuse at the edges, making a stronger solid without fully melting them.
Technically: Sintering is the thermal bonding of particulate material at temperatures below the bulk melting point, driven by diffusion across particle contact surfaces and the resulting reduction in surface energy. In iron and base-metal processing it is used to agglomerate fine ore or concentrate into a porous, mechanically stable burden suitable for blast or shaft furnace charging. The term is also applied in powder metallurgy and ceramics manufacturing, where the same physical mechanism produces dense, near-net-shape components; in those contexts it is sometimes confused with hot pressing, which additionally applies mechanical load.
Processing
skarn
A rock formed when hot fluids from a cooling magma bake and chemically change the surrounding limestone, often leaving behind concentrations of metal minerals in the process.
Technically: A skarn is a metasomatic rock produced by the reaction of high-temperature hydrothermal or magmatic fluids with carbonate-bearing country rocks, typically limestone or dolomite, resulting in a mineral assemblage dominated by calcium, magnesium, iron, and aluminium silicates such as garnet, pyroxene, and wollastonite. Economically, skarns host deposits of iron, copper, tungsten, zinc, lead, and other metals precipitated during the metasomatic process. The term is sometimes misapplied to any contact-metamorphic rock; strictly, skarn requires evidence of significant chemical exchange with an external fluid, not simply recrystallisation by heat alone.
Geology
slag
The stony waste left over after smelting. When metal melts away from rock, the leftover rocky material floats on top and is poured off separately.
Technically: Slag is the silicate-dominated, non-metallic waste melt generated during smelting or converting, formed when fluxes such as silica or limestone react with gangue oxides and iron oxides at furnace temperature. It is tapped separately from the metal or matte phase because of its lower density and, once solidified, is discarded or used as construction aggregate depending on its chemistry. Slags always contain some residual metal values either dissolved or as mechanically entrapped droplets, and their management—including re-processing of high-metal slags—is a standard part of smelter operations.
Processing
smelting
Melting a mineral concentrate at very high temperatures, sometimes with added materials, so that metal separates from the remaining waste. It is like melting a mixture in a bowl until the metal sinks away from everything else.
Technically: Smelting is a high-temperature pyrometallurgical process in which a sulfide or oxide feed is reacted—typically with a flux and, for sulfides, with oxygen—to produce a crude metal or metal-bearing matte that separates by density from a waste silicate melt called slag. For copper sulfide concentrates the immediate product is matte rather than metal; for iron ore the product is pig iron. Smelting is frequently confused with melting: melting simply changes a substance from solid to liquid without chemical reaction, whereas smelting involves chemical reduction or oxidation that changes the composition of the material.
Processing
solvent extraction
A chemical trick for moving metal out of a watery liquid and into an oily liquid, and then back into a different watery liquid—each time making the metal more concentrated and purer.
Technically: Solvent extraction, also called liquid–liquid extraction, transfers a target metal from a dilute aqueous pregnant leach solution into an organic solvent containing a selective extractant reagent, concentrating the metal and separating it from impurities that remain in the aqueous raffinate. The loaded organic phase is then contacted with a strong aqueous strip solution, releasing the metal at high concentration into the strip liquor, which is fed to electrowinning. In copper production the paired process is routinely abbreviated SX-EW (solvent extraction–electrowinning); solvent extraction is the purification and concentration step, while electrowinning is the deposition step, and the two should not be conflated.
Processing
spheronisation
A manufacturing step that rolls irregular particles of material into small, smooth balls, a bit like rolling scraps of dough into beads, so they pack together neatly and behave consistently.
Technically: Spheronisation is a size-enlargement process in which irregularly shaped granules or extrudates are tumbled at speed against a rotating friction plate, reshaping them into near-spherical pellets of controlled diameter and density. In battery-anode manufacture it is applied to graphite to improve packing density and electrolyte contact; in pharmaceutical processing it produces pellets of uniform flow and dissolution characteristics. The term is sometimes loosely applied to any pelletising step, but strictly it refers to the rounding of already-formed granules rather than the agglomeration of fine powder.
Processing
spodumene concentrate
A grey or white powder made by crushing and sorting lithium-bearing rock so that the useful mineral, spodumene, is separated from most of the worthless rock around it.
Technically: Spodumene concentrate is the product of physical beneficiation — typically crushing, dense-media separation and flotation — of spodumene-bearing pegmatite ore. The process upgrades the lithium aluminium silicate mineral spodumene relative to gangue minerals such as feldspar and quartz, producing a concentrate suitable for further chemical conversion to battery-grade lithium carbonate or lithium hydroxide. Spodumene concentrate is distinct from ore on one side of the value chain and from refined lithium compounds on the other; it is an intermediate traded commodity and its grade is typically reported in Li₂O percent rather than as LCE.
Materials
sponge metal
A lumpy, porous form of a pure metal produced straight from a chemical reaction — it looks a bit like a sponge because gas escaped while it was forming, leaving small holes throughout.
Technically: Sponge metal is the porous, irregularly structured form of a metal obtained by reducing a metal halide or oxide at high temperature without fully melting the product, leaving a solid mass riddled with interconnected voids where the by-product gases or salts were generated and escaped. Titanium sponge, produced by the Kroll process from titanium tetrachloride, and zirconium sponge are the most commercially significant examples. The product must be crushed, blended, and either melted or compacted by powder-metallurgy routes before it can be used; its porous character makes it an intermediate rather than a finished metal, and its composition and particle-size distribution are the principal quality parameters reported in trade.
Processing
spot price
The price you would pay today to buy something and have it delivered very soon, rather than agreeing a price now for delivery much later.
Technically: The spot price refers to the current market price for immediate or near-term delivery of a commodity, conventionally settlement within two business days for many exchange-traded metals. It contrasts with forward or futures prices, which are agreed now but apply to delivery at a specified future date. In practice, the term is applied loosely: for commodities without a liquid exchange, 'spot' may mean a short-term physical transaction concluded at an assessed or negotiated price rather than a standardised exchange contract, and the distinction from 'prompt' pricing is often context-dependent.
Markets
stockpile
A stored reserve of a material held ready for later use, like a pantry stocked before a long winter.
Technically: An accumulated physical inventory of a mineral or metal held by a government, producer, consumer or trader in anticipation of future demand, supply disruption or price movement. Stockpiles may be strategic, held by national authorities for security of supply purposes, or commercial, held by companies as working inventory or as a speculative position. The term is occasionally confused with in-ground resource, which describes material not yet extracted; a stockpile by definition refers to material already mined and available above ground.
Markets
stope
A stope is the underground cavity left behind after miners have dug out a body of ore. Think of it like a room carved inside a mountain where the valuable rock used to be.
Technically: A stope is the excavated void created by the extraction of ore in underground mining, bounded by the ore limits and the surrounding waste rock or fill. Stopes are distinguished from development headings in that they are the primary production excavations rather than access or infrastructure tunnels. Their geometry — whether open, shrinkage, cut-and-fill or sub-level — is dictated by the geometry and competence of the orebody and the host rock.
Mining
stratabound
A mineral deposit that is confined to a particular layer or set of layers in the rock, running roughly parallel to the surrounding beds rather than cutting across them.
Technically: A stratabound deposit is one whose mineralisation is largely or entirely contained within a specific stratigraphic unit or set of units, following bedding rather than cutting across it. The term does not necessarily imply that the deposit formed at the same time as the enclosing sediments (syndiagenetic); it may have been introduced later but was controlled by the permeability or chemistry of the host stratum. Stratabound is sometimes conflated with 'stratiform', but the latter implies a planar, layer-parallel geometry of the mineralisation itself, whereas stratabound refers only to stratigraphic confinement regardless of internal geometry.
Geology
strategic material
A material that a government considers so important for defence or the wider economy that it makes special plans to ensure it does not run out.
Technically: Strategic material is a policy designation, not a technical one, applied to substances whose absence would impair military capability or essential industrial production in ways that cannot quickly be corrected by market mechanisms. The term overlaps heavily with critical mineral but is broader: it may include processed forms, alloys or compounds rather than raw minerals, and the designation is typically made by a government or defence authority rather than by industry.
Materials
streaming
A deal where a company gives a mine money upfront and in return gets the right to buy a portion of what the mine produces — often silver or gold — at a fixed low price for years to come.
Technically: A streaming agreement is a financing arrangement in which a streaming company provides an upfront payment to a mining operation in exchange for the contractual right to purchase a portion of future metal production, usually a precious metal produced as a by-product, at a predetermined price that is typically well below the prevailing spot price. The streaming company profits from the spread between its contracted purchase price and the market price; the mining operator gains capital without issuing equity or incurring conventional debt. Streaming is distinct from a royalty in that the streaming company takes physical delivery of metal rather than receiving a percentage of revenue or profit.
Markets
strip ratio
In an open-pit mine, the strip ratio tells you how many tonnes of useless rock must be moved to reach each tonne of ore. A high strip ratio means a lot of digging for a little ore.
Technically: Strip ratio, expressed as tonnes of waste per tonne of ore, is the primary measure of mining dilution in open-pit operations and a principal determinant of operating cost. As a pit deepens or extends laterally, the strip ratio typically rises, eventually reaching a point at which mining the marginal increment of ore is uneconomic and the pit limit is defined. Strip ratio should not be confused with dilution, which refers to the blending of waste or low-grade material into the ore stream, though both affect the effective grade processed.
Geology
substitution
Swapping one material for a different one that can do the same job well enough — the way stainless steel cutlery replaced silver cutlery for most people.
Technically: The replacement of one material by another in a given application, driven by cost, availability, performance requirements or policy constraints. In supply-chain analysis, substitution potential is assessed along two dimensions: technical feasibility, meaning whether an alternative material can match the functional requirements of the incumbent, and economic feasibility, meaning whether the switch is competitive at prevailing or plausible future prices. Partial substitution, where a material is displaced from some end uses but not others, is more common than complete displacement, and the two should be distinguished when assessing the supply-demand implications for a specific mineral.
Markets
superalloy
A specially made metal alloy that keeps its shape and strength even when it is red-hot, used in things like jet engines and gas turbines.
Technically: A superalloy is a nickel-, cobalt- or iron-based alloy engineered to maintain mechanical integrity, oxidation resistance and creep resistance at temperatures that represent a substantial fraction of the alloy's own melting point. In practice the term almost always refers to nickel-base compositions, which dominate high-pressure turbine blades and other hot-section components. Superalloy should not be confused with refractory metal: refractory metals are elemental or simple alloys with extreme melting points, whereas superalloys are complex multicomponent systems whose performance depends on a controlled microstructure, particularly gamma-prime precipitate strengthening.
Materials
supergene enrichment
A natural process where rainwater seeping into a mineral deposit dissolves metals near the surface and carries them downward, leaving behind a richer, concentrated zone deeper in the ground.
Technically: Supergene enrichment occurs when oxidising meteoric water descends through a primary sulphide deposit, dissolves metals such as copper, and reprecipitates them at or below the water table as secondary sulphide or native-metal minerals, forming a zone of elevated grade above the unaltered primary ore. The overlying oxidised zone, from which metals have been leached, is termed the oxide cap or gossan. Supergene enrichment is frequently confused with secondary mineralisation in general; the specific distinction is that supergene processes are driven by downward-percolating surface water operating at low temperature, in contrast to hypogene (primary) mineralisation introduced from depth by hydrothermal fluids.
Geology
tailings
Tailings are the ground-up rock left over after the valuable minerals have been removed at a processing plant. The material is usually a wet, fine-grained slurry and has to be stored somewhere safe.
Technically: Tailings are the finely comminuted residue remaining after the target mineral or metal has been extracted from crushed and milled ore during mineral processing. They are distinct from waste rock in that they have passed through the mill and are typically fine-grained and often discharged as a slurry. Because tailings may contain residual reagents, heavy metals and sulfide minerals, their geochemical character — particularly their acid-generating potential — governs storage and long-term closure requirements.
Mining
tailings dam
A tailings dam is a large engineered embankment built to hold the wet waste material from a mine's processing plant. Unlike a water dam built all at once, it is usually raised in stages over the life of the mine.
Technically: A tailings dam, more precisely termed a tailings storage facility (TSF), is an engineered containment structure designed to impound tailings slurry and allow the water fraction to be decanted or evaporate for reuse or controlled release. TSFs differ fundamentally from conventional water-retention dams in that they are frequently raised incrementally using the tailings themselves or derived materials, and their structural properties change as the impounded material consolidates. The method of raise construction — upstream, downstream or centreline — has direct implications for seismic stability and failure risk, and is the primary technical distinction drawn in regulatory and engineering assessments.
Mining
unconformity
An unconformity is a buried surface where a gap in time exists between two layers of rock — older rocks were worn away before new ones formed on top, leaving a kind of missing chapter in the rock record.
Technically: An unconformity is a surface of contact between rock units that represents a significant hiatus in geological time, caused by erosion, non-deposition, or tectonic uplift of the older sequence before deposition of the younger one resumed. In mineral exploration, unconformities are structurally and chemically significant because they can act as pathways for hydrothermal fluids and as chemical or permeability traps that localise ore; the Athabasca Basin unconformity-type uranium deposits are the canonical example. Three main varieties are recognised — angular unconformity, disconformity, and nonconformity — distinguished by whether bedding above and below is parallel and whether the lower unit is sedimentary or crystalline.
Geology
underground mining
Mining that happens beneath the surface, reached by tunnels or shafts, so that workers and machines operate inside the rock rather than in the open air.
Technically: A collective term for any extraction method in which ore is won from workings wholly enclosed within the earth's crust, accessed by shafts, adits, or declines. Underground methods are selected when the orebody is deep, narrow, or high-grade enough that removing the overlying waste rock in an open pit would be uneconomic or impractical. The category encompasses a wide range of techniques — including room and pillar, longwall, cut-and-fill, and block caving — each suited to particular combinations of ore geometry, rock strength, and required production rate.
Mining
vein
A sheet-like filling of minerals occupying a crack in older rock, like a seam of material running through a block of stone.
Technically: In geology, a vein is a tabular body of minerals deposited by fluids that have crystallised within a fracture or fault in the host rock, typically under hydrothermal conditions. Veins are distinguished from dykes by their mineral (not igneous) fill, and from sedimentary layers by their cross-cutting or discordant relationship to surrounding strata. In economic geology, the term carries the specific implication that the mineralised fill is spatially discrete and bounded, which has direct consequences for how tonnage and grade are estimated during resource definition.
Geology
waste rock
Waste rock is rock that has to be moved to reach the ore but does not contain enough valuable mineral to be worth processing. It is usually piled up on the surface near the mine.
Technically: Waste rock is material excavated during mining that does not meet the cut-off grade required for processing and is therefore discarded, typically to surface dumps. It is distinguished from tailings by the fact that it has not been milled: it remains coarse-grained and has not been subjected to processing reagents. Where waste rock contains sulfide minerals, oxidation upon exposure to air and water can generate acid mine drainage, making the geochemical characterisation of waste rock a standard component of environmental assessment.
Mining
yellowcake
A dry, powdery solid — usually yellow or orange — made by extracting uranium from ore and drying it out. It is the form in which uranium leaves a mine before further processing.
Technically: Yellowcake is the conventional name for partially refined uranium oxide concentrate, principally triuranium octoxide (U₃O₈) or ammonium diuranate depending on the precipitation process used, produced at or near a uranium mine by leaching ore, purifying the resulting solution, precipitating the uranium, and drying the solids. It represents the first saleable product in the nuclear fuel cycle and the standard unit in which uranium is traded and reported. The colour ranges from yellow to orange to dark brown depending on the drying temperature and chemical composition, so the name is not always literally accurate; the term persists as a recognised commercial and regulatory designation rather than a precise chemical description.
Processing