What is the triclinic crystal system ?

Triclinic crystal system : definition

The triclinic system is a crystalline system whose unit cell is a right prism in which the crystallographic axes a, b and c are of different lengths, and whose angles, all distinct, are different from 90°. It includes 2 crystalline classes ; the hemihedral class, which has no elements of symmetry, has very few representatives in nature.

Quite a few minerals (about 2% of the mineral kingdom) are triclinic, including microcline, kyanite, pectolite, turquoise, axinite, and plagioclase...

Certain triclinic cells can be pseudocubic, pseudoquadratic, pseudo-orthorhombic, pseudorhombohedral, pseudomonoclinic or pseudohexagonal due to the bringing together of the triclinic cell with other crystalline cells.