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.
Technisch gezien: 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.
Technisch gezien: 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
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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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.
Technisch gezien: 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