Tetragonal system

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The tetragonal crystal system has three axes of symmetry: two axes, of equal length, lie in a plane at 90°; the third is longer or shorter and is at right angles to the others.

Crystals are often long and slender or even needle-like; characteristic forms are four-sided prisms, pyramids, and dipyramids.

Sources

  • Chesterman, Charles W. The Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf: New York (1987). pp. 33-34