What is a crystal class in mineralogy ?

Crystal class : definition

A crystal class, also called a symmetry class, groups together a set of minerals that have the same elements of symmetry and therefore share a community of crystalline forms.

The 7 crystal systems of the mineral kingdom are divided into 32 crystal classes :

- 2 for the triclinic system
- 3 for the monoclinic system
- 3 for the orthorhombic system
- 7 for the hexagonal system
- 5 for the rhombohedral system
- 7 for the tetragonal system
- 5 for the cubic system