Examples of ores containing critical metals

Petalite

Petalite is an extensively mined mineral in some locations (e.g., Bikita, Zimbabwe, Namibia) and is composed of lithium, aluminum, silica and oxygen (LiAl(Si₄O₁₀)) and is common in pegmatites (late-stage felsic igneous rocks). Petalite can range in color from translucent to white, pink or grey. The name petalite is derived from the Greek word for leaf “petalon” because of its cleavage. Lithium and aluminum in petalite are commonly replaced (substitution) by magnesium, iron, sodium and potassium.

Spodumene

Spodumene is also an important lithium-bearing mineral that is composed of lithium, aluminum, silica and oxygen. However, although chemically similar to petalite, it has a different chemical formula: LiAlSi₂O₆. This mineral is also common in lithium-rich pegmatites and mined in e.g., China, Australia, Sweden and Congo. It ranges in color between translucent, yellow, green, pink, purple, white and grey. Aside from its value as an ore mineral, spodumene is also desired as a gemstone because of its range in color and vitreous lustre. Elements in spodumene are commonly substituted by iron, manganese, sodium, and potassium.

Chalcopyrite

Chalcopyrite is an important copper ore mineral composed of copper, iron and sulphur (CuFeS₂). It is mined on many locations all over the world. Copper and iron in chalcopyrite are also occasionally replaced by cobalt, silver or gold that in certain cases can be extracted as a by-product besides copper. Chalcopyrite has a brass yellow color that is often combined with an iridescent tarnish. It occurs mainly in veins and in disseminated patches within igneous or hydrothermally altered rocks.

Magnetite

Magnetite is the most important iron oxide mineral with the chemical formula Fe₂O₄. It is strongly magnetic and commonly mined for iron all over the world. The mineral is opaque and greyish black to black with a metallic lustre. It often hosts zinc, manganese, nickel or titanium as substituting elements that in certain cases can be extracted as by-products besides iron. Magnetite is most known for its occurrence in banded iron formations (BIFs), but it also forms in igneous and hydrothermally altered rocks.

Hematite

Hematite is similar in composition to magnetite; it is also an iron oxide but has less oxygen than magnetite (Fe₂O₃). Hematite can vary a lot in appearance both in color and shape. It has a color range of steel gray to black, and dark brown to a bright red rusty color. It occurs as well-shaped crystals, to rounded aggregates and nodules. Like magnetite, it is commonly mined for its iron content with by-products of titanium and manganese. Mining of hematite occurs in e.g., Canada, Brazil and Venezuela. It frequently leaves reddish stains since the iron in hematite is oxidised. Hematite occurs in most geological settings.

Galena

Galena is the most common lead bearing ore mineral and is mined in e.g., Sweden, South Africa, Russia, and Canada. It consists of lead and sulphur (PbS) and has a high density; therefore, it is a heavy mineral. It has a silver-gray color and is usually found in hydrothermally altered rocks in association with other sulphide minerals and can host silver, copper and iron as substituting elements for lead.

Pentlandite

Pentlandite is a mineral that is composed of nickel, iron and sulfur and varies in its iron and nickel content (Ni_xFe_y)₉S₈. It is commonly mined for nickel, but cobalt, silver and copper that occur as substituting elements can in certain cases also be extracted as by-products. The nickel mining commences at e.g., Canada, Indonesia, South Africa, and Russia. Pentlandite occurs in mafic rocks and is usually intergrown with other sulphide minerals. It has a yellow to bronze color and it is non-magnetic which sets it apart from other brass-colored minerals.

Cobaltite

Cobaltite consists of cobalt, arsenic and sulphur (CoAsS). Its name originates for the German word Kobold, which means goblin because it was believed to be bewitched because the mineral could not be melted. It is the main mineral mined for cobalt in hard rock where cobalt is not extracted as a by-product in other base metal deposits and mainly mined in Australia, China and Russia. It is an opaque mineral and occurs in the colors reddish silver, steel gray and black. Common substituting elements are copper, lead, iron and nickel. Cobaltite occurs in high temperature hydrothermally altered ore deposits.

Pyrite

Pyrite used to be mined for sulfuric acid but not anymore since nowadays sulfuric acid is extracted as a by-product from other industries. It has the nickname ‘fool’s gold’ because it is often mistaken for gold when present in rocks due to its gold-yellow color and metallic lustre. However, the chemical composition of pyrite does not contain gold, but iron and sulfur (FeS₂). Common substituting elements in pyrite are copper, cobalt, lead and nickel, which in certain cases can be extracted. When pyrite grains have time and space to crystallise, they form very recognisable cubes. It is one of the most common sulfide minerals, is often associated with the occurrence of ore bearing minerals and can occur in many geological settings.