The triclinic system is a crystal system of which the unit cell is a prism with crystallographic axes of different lengths (a b c) and of which the angles, which are all different (alpha = beta = gamma = 90 degrees), are different from 90 degrees. It includes two symmetry classes; the hemihedral class, which has no symmetry element and has no occurrences in nature.
The triclinic system is one of the seven crystal systems, together with:
Rhodonite is a crystal in the triclinic system. © DR