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.
Технически: 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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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
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.
Технически: 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.
Технически: 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
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.
Технически: 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
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.
Технически: 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