Changes

'''Crystal systems''' are a way of characterising the three-dimensional shape shape of mineral crystals by their symmetry and thus aiding in their classification. Mineral crystals come in a seemingly infinite range of shapes. But behind this tremendous diversity of form there is a strict order, because crystals always grow according to simple mathematical laws.<ref>Chesterman, Charles W. ''The Audubon Society Field Guide to North American Rocks and Minerals'', Alfred A. Knopf: New York (1987) ''p. 33''</ref>

'''Crystal systems''' are a way of characterising the three-dimensional shape of mineral crystals by their symmetry, thus aiding their classification. Mineral crystals come in a seemingly infinite range of shapes, but behind this tremendous diversity of form there is a strict order, because crystals always grow according to simple mathematical laws.<ref>Chesterman, Charles W. ''The Audubon Society Field Guide to North American Rocks and Minerals'', Alfred A. Knopf: New York (1987) ''p. 33''</ref>

There are 6 (or 7)<ref>U.S. classification usually put [[trigonal system|trigonal]] as a sub-set of the [[hexagonal system]], whereas, British practice is to make it a separate class.</ref> crystal systems:

There are 6 (or 7)<ref>U.S. classification usually put [[trigonal system|trigonal]] as a sub-set of the [[hexagonal system]], whereas British practice is to make it a separate class.</ref> crystal systems:

*[[Hexagonal system|Hexagonal]], requires 1 sixfold axis of rotation.  

*[[Hexagonal system|Hexagonal]], requires 1 sixfold axis of rotation.  

*[[Triclinic system|Triclinic]], all cases not satisfying the requirements of any other system; thus there is no other symmetry than translational symmetry, or the only extra kind is inversion.

*[[Triclinic system|Triclinic]], all cases not satisfying the requirements of any other system; thus there is no other symmetry than translational symmetry, or the only extra kind is inversion.

==Notes & References==

==Notes & references==

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[[Category:Crystallography]]

[[Category:Crystallography]]