An example of the hexagonal crystals, beryl

Hexagonal

In crystallography, the hexagonal is one of the 7 crystal systems. It contains 7 point groups . It has the same symmetry as a right prism with a hexagonal base. There is only one hexagonal Bravais lattice, which has six atoms per unit cell.

Graphite is an example of a crystal that crystallizes in the hexagonal crystal system.

Hexagonal arrangements have also been observed in systems of amphiphiles and constitutes one of the types of lipid polymorphism.

The point groups (crystal classes) that fall under this crystal system are listed below, followed by their representations in Hermann-Mauguin or international notation and Schoenflies notation, and mineral examples, if they exist.

name	international	Schoenflies	example
dihexagonal bipyramidal		D6h	beryl
dihexagonal pyramidal		C6v	greenockite
hexagonal bipyramidal		C6h	apatite
hexagonal pyramidal		C6	nepheline
hexagonal trapezohedral		D6	kalsilite and high quartz
ditrigonal bipyramidal		D3h	benitoite
trigonal bipyramidal		C3h	none

See also

• Crystal structure
• Close-packing (hcp)
• Wurtzite (crystal structure)

References

• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., pp. 78 - 89, ISBN 0-471-80580-7