Difference between revisions of "Hexagonal (or Trigonal) System"
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| − | 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 | + | 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 rounded [[triangular]] or [[hexagonal]] cross section; characteristic forms are three- or six-sided [[ | + | [[Crystals]] are generally [[prismatic]] or [[columnar]], with a rounded [[triangular]] or [[hexagonal]] 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= | ||
*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) | ||
[[category:geometry]] | [[category:geometry]] | ||
Revision as of 13:59, May 23, 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)