Critical minerals and their uses

Properties
High-purity alumina (HPA) is a high-purity, white crystalline powder form of aluminium oxide (Al₂O₃) characterised by its purity levels (i.e. 99.99% Al₂O₃). HPA is chemically stable, has a high melting point, high hardness, good thermal conductivity and high electrical insulation.

Usages
HPA is used in the automotive and aerospace sector and is an important component of lithium-ion batteries and high performance electronics and optics.

Geological Occurrence
Crustal abundance of aluminium is 81,300 ppm. However, HPA is predominately refined from kaolin clays and aluminium metal feedstock.

Mineral system group
Sediment hosted.

Extraction
Main product (kaolin) or by-product from metals refining.

Properties
Silvery-white, shiny, very brittle metal that is a semiconductor and resistant to acids.

Usages
Antimony is used in flame retardants, as an alloying material for lead and tin, and in micro-capacitors.

Geological Occurrence
Crustal abundance is 0.2 ppm; major antimony-bearing minerals include stibnite and tetrahedrite.

Mineral system group
Porphyry-epithermal, subaqueous volcanic-related, orogenic and basin-hosted.

Extraction
Main product or co-product (with gold).

Properties
Arsenic is a metalloid. It has three allotropes: grey, black, and yellow. Grey is the most common, and is a tin-white colour, which oxidises dark grey to black. Grey arsenic is solid and brittle under standard conditions and has low electrical and thermal conductivity.

Usages
Arsenic is primarily used as an alloy of lead for lead car batteries and ammunition. It is also widely used as a dopant in semiconductors. It is also a component of the semiconductor compound gallium-arsenide.

Geological Occurrence
Crustal abundance is approximately 1.5ppm. Present in many lead–zinc and copper ores, most commonly in the mineral arsenopyrite. It is also common in orogenic gold systems where arsenic minerals, along with pyrite, often host gold in refractory gold ores.

Mineral system group
Mesothermal and epithermal veins. Occasionally in metamorphic dolomite rocks.

Extraction
Arsenic can be obtained from copper, gold, and lead smelter flue dust as well as from roasting arsenopyrite.

Properties
Steel-grey, low-density metal that is hard and brittle at room temperature, is highly toxic and has a high melting point (1,287 °C).

Usages
Beryllium is used in telecommunications equipment, automotive electronics, and aerospace, defence and industrial components.

Geological Occurrence
Crustal abundance is 1.9 ppm; major beryllium-bearing minerals include bertrandite, beryl, chrysoberyl and phenakite.

Mineral system group
Granite-related.

Extraction
Main product.

Properties
Silvery-white brittle metal that has low thermal conductivity and is diamagnetic.

Usages
Bismuth is often used in free-machining steels, brass, pigments, solders (as a non-toxic replacement for lead) and pharmaceuticals. It is also used as an additive to enhance metallurgical quality in foundry applications and as a triggering mechanism in fire sprinklers.

Geological Occurrence
Crustal abundance is 0.18 ppm; major bismuth-bearing minerals include bismuthinite. Bismuth can also be an important trace to minor constituent in galena.

Mineral system group
Porphyry-epithermal, granite-related, subaqueous volcanicrelated, orogenic and basin-hosted.

Extraction
By-product of lead smelting.

Properties
Hard metal with a high melting point (1,907 °C) that is resistant to tarnish. Chromium is antiferromagnetic at room temperature and paramagnetic above 38 °C. It is passivated by oxygen, making it stable to acids.

Usages
Chromium is used in stainless and heat-resistant steels, superalloys, non-ferrous alloys and pigments.

Geological Occurrence
Crustal abundance is 135 ppm. Chromium-bearing minerals include chromite.

Mineral system group
Mafic-ultramafic orthomagmatic and surficial.

Extraction
Main product.

Properties
Ferromagnetic metal that is hard and lustrous.

Usages
Emerging technologies that could use cobalt include lithium batteries and synthetic fuels. The most important present use is in superalloys, steel and pigments.

Geological Occurrence
Crustal abundance is 26.6 ppm; major cobalt-bearing minerals include cobaltite and cobaltian pyrite.

Mineral system group
Mafic-ultramafic orthomagmatic and basin-hosted.

Extraction
By-product, co-product of copper mining.

Properties
Fluorine is pale yellow, highly reactive, and is a toxic gas under standard conditions.

Usages
Fluorine is used in lithium batteries, semiconductor manufacturing, electrical insulation, and solar panels. Other uses include Teflon manufacture, uranium processing and steel and aluminium manufacturing, cement, and rocket propellants.

Geological Occurrence
Crustal abundance is 553 ppm. A major fluorine bearing mineral is fluorite.

Mineral system group
Granite-related and basin-hosted.

Extraction
Fluorine is sourced from the mineral fluorite (or fluorspar). Fluorite is sourced from large hydrothermal veins containing silver, lead, zinc, copper, and other metals. It is also found in carbonate rocks.

Properties
Silvery-white metal that has a low melting point (29.7 °C), a high boiling point (2,204 °C) and is a semiconductor.

Usages
Gallium is used in integrated circuits, laser diodes, LEDs, photodetectors and thin layer photovoltaics.

Geological Occurrence
Crustal abundance is 16 ppm; in nature gallium occurs as a trace element in bauxite and sphalerite.

Mineral system group
Subaqueous volcanic-related; orogenic basin-hosted and surficial.

Extraction
By-product of alumina refining and zinc mining.

Properties
Grey-white metalloid that is hard, lustrous and semiconducting.

Usages
Germanium is used in fibre and infrared optics, as a polymerisation catalyst and in electronic and solar electric applications.

Geological Occurrence
Crustal abundance is 1.3 ppm; in nature germanium occurs as a trace element in sphalerite and coal.

Mineral system group
Subaqueous volcanic-related, orogenic and basin-hosted.

Extraction
By-product of zinc processing.

Properties
Iron-black mineral with a metallic-earthy lustre that is an electrical and thermal conductor, has high thermal resistance, is inert and can be used as a lubricant.

Usages
Uses of graphite include carbon-graphite composites, electronics, foils, friction materials and special lubricants applications. Flexible graphite products and large-scale fuel cell application developments may become high users of graphite.

Geological Occurrence
Crustal abundance is 1,800 ppm (total C). In nature, graphite is one of a number of forms of carbon.

Mineral system group
(Metamorphosed) basin-hosted.

Extraction
Main production.

Properties
A shiny, silvery, corrosion-resistant metal.

Usages
Hafnium is used in the control rods of nuclear reactors, and in vacuum tubes, and has been used as an alloying agent with iron, titanium, niobium and other metals. Hafnium oxide may be used as an electrical insulator in microchips.

Geological Occurrence
Crustal abundance is 5.8 ppm. Substitutes for zirconium, especially in zircon.

Mineral system group
Heavy mineral sands, pegmatites, carbonatite intrusions.

Extraction
By-product, co-product of zircon mining.

Properties
Silvery-white, dense metal that forms alloys with most other metals and generally increases strength, corrosion resistance and hardness.

Usages
Indium tin oxide (ITO) thin-film coatings are used for electrically conductive purposes in flat-panel, TV and smartphone devices. Other uses include electrical components and semiconductors, solders, alloys and compounds.

Geological Occurrence
Crustal abundance is 0.052 ppm; indium occurs mostly as a trace element in sphalerite.

Mineral system group
Subaqueous volcanic-related, orogenic and basin-hosted.

Extraction
By-product of zinc-lead, copper and tin mining and smelting.

Properties
Shiny, silvery, tough and soft metal that forms strong alloy, is very reactive and has the lowest density of all known solids at room temperature.

Usages
Lithium is used in batteries, ceramics and glass.

Geological Occurrence
Crustal abundance is 16 ppm; lithium occurs mostly in spodumene and lepidolite, but also in salt lake and oil field brines.

Mineral system group
Intrusion-related and surficial.

Extraction
Main product.

Properties
Shiny, grey, light metal.

Usages
Magnesium is used in aluminium alloys, die-casting (alloyed with zinc), removal of sulphur during the production of iron and steel, and the production of titanium.

Geological Occurrence
Magnesium is the seventh most abundant element in the Earth’s crust at about 2.5%.

Mineral system group
Metamorphosed mafic-ultramafic orthomagmatic and basin-hosted.

Extraction
Extracted from dolomite, talc and magnesite; main product.

Properties
Silvery-grey metal that is hard, very brittle and paramagnetic.

Usages
Manganese is alloyed in steel and aluminium, and is used in batteries and fertiliser.

Geological Occurrence
Crustal abundance is 770 ppm; the main manganese mineral is pyrolusite.

Mineral system group
Basin-hosted and surficial.

Extraction
Main product.

Properties
Molybdenum is a lustrous silver-white metal that has high mechanical strength, a low coefficient of thermal expansion and good heat conductivity.

Usages
Molybdenum is used in renewable energy (wind turbines, solar panels, and geothermal plants) and aerospace (jet and rocket engines and radiation shields).

Geological Occurrence
Crustal abundance is approximately 1.5ppm. Mined as a primary ore, but also recovered as a byproduct of copper and tungsten mining. The main commercial source is molybdenite.

Mineral system group
Porphyry-epithermal, granite-related and iron-oxide copper-gold.

Extraction
Molybdenum is mined as a principal ore and is also recovered as a byproduct of copper and tungsten mining. The main commercial source is molybdenite.

Properties
Hard, ductile and malleable metal.

Usages
Stainless and heat-resistant steel production used in chemical industries, motor vehicles, medical applications, electronic engineering and construction. Nickel is also used in lithium-ion batteries for electric vehicles, non-ferrous alloys and electroplating.

Geological Occurrence
Crustal abundance is 59 ppm; the major Ni-bearing minerals include pentlandite, millerite and violarite.

Mineral system group
Mafic-ultramafic orthomagmatic and surficial.

Extraction
Main product.

Properties
Soft and ductile metal with good resistance to organic and inorganic acids.

Usages
Niobium is used in micro-capacitors, steel and ferroalloys.

Geological Occurrence
Crustal abundance is 8 ppm; niobium occurs as a minor element in minerals such as columbite, pyrochlore and euxinite.

Mineral system group
Granite-related and alkaline intrusion-related.

Extraction
Co-product, by-product.

Properties
Metals characterised by catalytic properties, resistance to wear, tarnish and chemical attack, and by stable electrical properties.

Usages
Platinum and palladium are both used in catalytic converters. Platinum is used in electronic applications and fuel cells, and palladium is used in seawater desalination.

Geological Occurrence
Crustal abundances of platinum-group elements are 0.57 ppb (ruthenium), 0.2 ppb (rhodium), 1.5 ppb (palladium), 0.041 ppb (osmium), 0.037 ppb (iridium) and 1.5 ppb (platinum). Platinum-group elements occur as metallic alloys, sulfide and arsenide minerals.

Mineral system group
Mafic-ultramafic orthomagmatic, alkaline intrusion-related and surficial.

Extraction
Main product, by-product.

Properties
The 15 lanthanide elements plus yttrium are here grouped as rare-earth elements (chemists often include scandium). These 16 rare-earth elements have a variety of properties.

Usages
Rare-earth elements are used in magnets, catalysts, metal alloys, polishing powders, phosphors, energy storage and superconductors.

Geological Occurrence
Crustal abundances are 31 ppm (yttrium), 20 ppm (lanthanum), 43 ppm (cerium), 4.9 ppm (praseodymium), 20 ppm (neodymium), 3.9 ppm (samarium), 1.1 ppm (europium), 3.7 ppm (gadolinium), 0.6 ppm (terbium), 3.6 ppm (dysprosium), 0.77 ppm (holmium), 2.1 ppm (erbium), 0.28 ppm (thulium), 1.9 ppm (ytterbium), and 0.30 ppm (lutetium). Rare-earth elements occur as minor to trace elements in many minerals, but major rare-earth elementbearing minerals include carbonates (e.g. bastnäsite), phosphates (e.g. monazite, xenotime) and silicates (e.g. allanite).

Mineral system group
Granite-related, iron-oxide copper-gold, alkaline intrusionrelated, surficial (lanthanides).

Extraction
Main product, co-product.

Properties
Very dense metal with a very high melting point (3,186 °C).

Usages
Rhenium is used in superalloys for high-temperature turbine engine components and in catalytic converters.

Geological Occurrence
Crustal abundance is 0.188 ppb; the major source of rhenium is as a minor element in molybdenite.

Mineral system group
Porphyry-epithermal and iron-oxide copper-gold.

Extraction
By-product.

Properties
A silvery-white metallic element.

Usages
Uses include in aluminium-scandium alloys, solid oxide fuel cells, ceramics, electronics, lasers, lighting and radioactive isotopes. Scandium isotopes may be used as tracing agents in oil refining.

Geological Occurrence
Average crustal abundance is 22 ppm.

Mineral system group
Mafic-ultramafic igneous-related mineral systems.

Extraction
By-product or main product.

Properties
Selenium is a metalloid. It has several allotropes that are created with temperature changes and the rate of temperature change. When prepared in chemical reactions, it forms a brick-red powder. Another allotrope, black selenium, is a brittle lustrous solid under standard conditions.

Usages
Selenium is used in solar panels, steel manufacturing, glass tinting, pigmentation in paints and ceramics, semiconductors (as hydrogen selenide), and alloys used in the creation, storage and transmission of energy such as electronic components and electrical rectifiers (converting AC to DC). It is also a component of lithium-selenium (Li-Se) batteries.

Geological Occurrence
Crustal abundance is approximately 0.13 ppm. The major source is as a minor element in chalcopyrite, but there are a large range of selenide, selenate, and selenite minerals.

Mineral system group
Porphyry-epithermal, granite-related, mafic-ultramafic orthomagmatic, iron-oxide copper-gold and subaqueous volcanic-related.

Extraction
Selenium is a by-product of copper and to a lesser extent, nickel.

Properties
Silicon is a metalloid with a blue-grey, metallic lustre.

Usages
Silicon is a widely used semiconductor material in micro-electronics and all electronic devices. It is also used in photovoltaics (solar panels), optical fibres, high performance ceramics and speciality glass applications.

Geological Occurrence
Crustal abundance of silicon is 277,200 ppm. However, it does not occur naturally in elemental form. Silicon is produced commercially from silica (SiO2) which must be >98% purity.

Mineral system group
Quartz related, silica sand deposits.

Extraction
Main product (silica).

Properties
Blue-grey, lustrous, hard, tough and ductile metal that is very resistant to corrosion from acids, has high thermal and electrical conductivity, and has a high melting point (3,107 °C).

Usages
Tantalum is used in electronic micro-capacitors and medical technology.

Geological Occurrence
Crustal abundance is 0.7 ppm; the major source of tantalum is tantalite and columbite, although there are a number of other rare tantalum minerals.

Mineral system group
Granite-related.

Extraction
Main product, co-product, by-product.

Properties
Metallic, silvery-white metalloid that is brittle and easily pulverised, and resists oxidation by air.

Usages
Tellurium is used in high efficiency photovoltaics and steel alloys, as well as x-ray and infrared detectors.

Geological Occurrence
Crustal abundance is approximately 1 part per billion (ppb); the major source of tellurium is a trace element in chalcopyrite, and it occurs in a large range of telluride minerals.

Mineral system group
Porphyry-epithermal, granite-related, mafic-ultramafic orthomagmatic, iron-oxide copper-gold subaqueous volcanic-related, and orogenic.

Extraction
Tellurium is a by-product of copper mining.

Properties
Low-density metal with high mechanical strength, high melting point, low thermal expansion coefficient and a high resistance to saltwater and acids.

Usages
Titanium is used in titanium oxide pigments, carbides and chemicals, and as an alloy in steel and superalloys.

Geological Occurrence
Crustal abundance is approximately 0.43%; the major source of titanium is ilmenite but other significant titanium minerals include titanite and rutile (and other TiO2 polymorphs).

Mineral system group
Mafic-ultramafic orthomagmatic and surficial.

Extraction
Main product, co-product.

Properties
Steel-grey metal that is brittle, and has a very high melting point (3,422 °C), the lowest vapour pressure (at temperatures above 1,650 °C) and the highest tensile strength. Tungsten has the lowest coefficient of thermal expansion of any pure metal.

Usages
Major uses of tungsten include electronic applications, lighting, construction, steel and alloys, and mining.

Geological Occurrence
Crustal abundance is approximately 1 ppm; the major source of tungsten are wolframite and scheelite.

Mineral system group
Granite-related and surficial.

Extraction
Main product.

Properties
Silver-grey ductile and malleable metal that is hard, not brittle, and has good resistance to corrosion and acids.

Usages
Vanadium is used as alloy in iron and steel, superalloys, chemical catalysts and batteries.

Geological Occurrence
Crustal abundance is approximately 138 ppm; the major source of vanadium is from vanadium-bearing magnetite, although it also occurs as vanadinite, carnotite and other uncommon minerals.

Mineral system group
Mafic-ultramafic orthomagmatic, basin-hosted and surficial.

Extraction
Co-product.

Properties
Soft metal that is resistant to corrosion, with a melting point of 1,855 °C and a boiling point of 4,371 °C.

Usages
Zirconium metal is used for cladding nuclear reactor fuels, and zirconium compounds are used in a variety of high-temperature applications, such as moulds for molten metals.

Geological Occurrence
Crustal abundance is approximately 132 ppm; the major source of zirconium is zircon (ZrSiO4), although there are a number of other minor to trace zirconium-bearing minerals.

Mineral system group
Alkaline intrusion-related and surficial (heavy mineral sand deposits).

Extraction
Main product, co-product.