Tetragonal

An example of the tetragonal crystals, wulfenite

In crystallography, the tetragonal crystal system is one of the 7 lattice point groups. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square base (a by a) and height (c, which is different from a).

There are two tetragonal Bravais lattices: the simple tetragonal (from stretching the simple-cubic lattice) and the centered tetragonal (from stretching either the face-centered or the body-centered cubic lattice).

Simple tetragonal

Body-centered tetragonal

The point groups that fall under this crystal system are listed below, followed by their representations in international notation and Schoenflies notation, and mineral examples.

Name	International	Schoenflies	Example
ditetragonal bipyramidal		D4h	rutile
ditetragonal pyramidal	4mm	C4v	diaboleite
tetragonal bipyramidal		C4h	scheelite
tetragonal pyramidal	4	C4	wulfenite
ditetragonal alternating		D2d	chalcopyrite
tetragonal trapezohedral	422	D4	phosgenite
tetragonal alternating		S4	cahnite

[edit] See also

• Crystal structure
• point groups
• Bravais lattices

[edit] References

• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., pp. 73 - 78, ISBN 0-471-80580-7