Difference between revisions of "Hexagonal (or Trigonal) System"
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*Chesterman, Charles W. ''The Audubon Society Field Guide to North American Rocks and Minerals'', Alfred A. Knopf: New York (1987) | *Chesterman, Charles W. ''The Audubon Society Field Guide to North American Rocks and Minerals'', Alfred A. Knopf: New York (1987) | ||
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Revision as of 14:07, May 25, 2007
Four axes of symmetry: three, of equal length, lie in a plane at 120°; the fourth axis is longer or shorter and is at right angles to the others.
Crystals are generally prismatic or columnar, with a rounded triangular or hexagonal cross section; characteristic forms are three- or six-sided prisms, pyramids, and rhombohedrons. The very similar trigonal system is often included within the hexagonal system. Chesterman, pp. 33-34
Sources
- Chesterman, Charles W. The Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf: New York (1987)