A naturally occurring homogeneous solid with a highly ordered lattice and of a defined chemical composition.

A diagenetic transformation of a mineral and itself or a polymorph, including differences in size and shape.

A chemical compound to exists as two or more forms whilst having the same chemical composition. For example, calcite and aragonite.

Silicate mineral composed of chains of silica tetrahedra. Cations occupy the sites between oxygen atoms. The general formula is:
A_1-x(B,C)_1-xT₂O₆.
A is commonly sodium or calcium, B is magnesium or iron (²⁺), C is aluminium or iron (³⁺) and T is silicon or aluminium. It is common in igneous and metamorphic rocks.

The most common silicate mineral. The chemical formula is SiO₂.

All silicate minerals have a structure based on the silica tetrahedra, an arrangement of 1 silica atom and 4 oxygen atoms. The chemical formula for this is SiO₄.

A mineral formed from silica and oxygen. The majority of rock forming minerals are silicates. Examples are quartz and pyroxene.

A polymorph whose other two minerals are kyanite and andalusite.

A crystal with concentric layers differing in chemical composition representing a complex crystallisation history.