Critical Minerals and their uses

High-purity Alumina

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.

Antimony

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).

Beryllium

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.

Bismuth

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.

Chromium

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.

Cobalt

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.

Gallium

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 zinc mining.

Germanium

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.

Graphite

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.

Hafnium

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.

Helium

Properties

Colourless, odourless, tasteless, non-toxic gas that has the lowest boiling and melting points of all the elements.

Usages

Helium is used in cryogenics, cooling systems, MRI scanners, LCD and fibre optics.

Geological occurrence

Helium, a product of radioactive decay of heavy elements, accumulates with natural gas in hydrocarbon traps.

Mineral system group

Basin-hosted.

Extraction

By-product of natural gas production.

Indium

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.

Lithium

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.

Magnesium

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.

Manganese

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.

Niobium

PropertiesSoft 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.

Platinum group elements

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.

Rare earth elements

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.

Rhenium

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.

Scandium

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.

High-purity Silicon

Properties

Non-combustible, colourless/white crystal.

Usages

High-purity Silica is a high-grade (>99.99% Silicon dioxide (SiO2)), raw ingredient used for semiconductors in electronics, computer processors, photovoltaics (solar panels), optical fibres, high performance ceramics and specialty glass applications.

Geological occurrence

Crustal abundance of silicon is 277,200 ppm. However, high-purity silica (<99.95% purity) is relatively rare in nature.

Mineral system group

Quartz related, silica sand deposits.

Extraction

Main product.

Tantalum

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.

Titanium

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.

Tungsten

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.

Vanadium

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.

Zirconium

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.