Difference between revisions of "Hexagonal (or Trigonal) System"
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Four [[Axis|axes]] of [[symmetry]]: three, of equal length, lie in a plane at 120°; the fourth axis is longer or shorter and is at [[right angle]]s to the others. | Four [[Axis|axes]] of [[symmetry]]: three, of equal length, lie in a plane at 120°; the fourth axis is longer or shorter and is at [[right angle]]s to the others. | ||
| − | [[Crystals]] are generally [[prismatic]] or [[columnar]], with a rounded [[triangular]] or [[ | + | [[Crystals]] are generally [[prismatic]] or [[columnar]], with a rounded [[triangle|triangular]] or [[hexagon]]al cross section; characteristic forms are three- or six-sided [[prism]]s, [[pyramid]]s, and [[rhombohedron]]s. The very similar ''[[trigonal system]]'' is often included within the hexagonal system. Chesterman, pp. 33-34 |
==Sources== | ==Sources== | ||
Revision as of 19:21, July 14, 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)