Hexagonal system
The hexagonal system is a crystal system of which the unit cell is a right prism on a lozenge-shaped base. A combination of three of these unit cells forms a hexagonal prism.
This system has two equal crystallographic axes (a = b) with an angle of 120 degrees between them; the third axis, c, is perpendicular to the plane formed by a and b (alpha = beta = 90 degrees). The characteristic element of the system is a 6-fold symmetry axis: A6. this system has 5 crystal classes.
The hexagonal system is one of the seven lattice systems along with:
Emerald is a crystal in the hexagonal system. © DR