Glossary :: Mineralogy

Amethyst

Variant of quartz, purple in colour.

Andalusite

A polymorph whose other two minerals are kyanite and sillimanite. A particularly notable variety of andalusite is chiastolite, which has crosses of carbon in it....More

Apatite

Phosphate mineral, which can be in three forms depending on its chemistry. Forms are Fluorapatite (fluorine-rich), Chlorapatite (chlorine-rich and Hydroxylapatite (rich in hyrdroxides). It is also what most teeth of mammals are made of!...More

Aragonite

A polymorph of calcite. Produced by many organisms as a shell, test or other hard part. Unstable at the Earth's surface and is very rare in ancient sediments.

Calcite

Calcium Carbonate (CaCO₃). Exists as two forms, low and high Mg. Only low Mg is stable at the Earth's surface.

Citrine

Variety of quartz. Yellow-orange in colour.

Cleavage

The distinct planes of weakness that a mineral breaks along.

Garnet

A cubic mineral of the general form of:A32+B23+Si3O12A can be magnesium, iron, manganese or calcium, B is iron or aluminium (occasionally chromium). Commonly found in metamorphic and occasionally igneous rocks....More

Isotropic

A mineral that is isotropic is one that appears black in thin section in both plane and polarised light.

Kyanite

A polymorph whose other two minerals are sillimanite and andalusite. Usually blue.

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