Crystal Systems

Crystals are minerals that display polyhedral geometrical symmetry, microscopically as well as to the naked eye.

Crystalline symmetry is produced by geological forces and atomic-level chemical interactions.

All minerals can become crystals, but rare, ideal conditions are needed to produce well-formed examples. Impurities alter the properties of all naturally formed crystals.

Crystals can take one or more of 15 cubic (also called isometric) forms, or one or more of 32 non-cubic (also called non-isometric) forms. The same crystal may exist in more than one form.

The six lattice systems of isometric and non-isometric crystal symmetry are cubic, hexagonal, tetragonal, orthorhombic, monoclinic and triclinic.

A seventh rhombohedral system is sometimes distinguished from the hexagonal system

Crystals may also be amorphous.

Many natural processes interact to form the array of crystal structures minerals take on.