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Merosymmetry versus merohedrism
Published online by Cambridge University Press: 14 March 2018
Extract
While crystal classes based upon symmetry furnish a clear-cut classification of crystals free from ambiguity and uncertainty, there are cogent reasons for recognizing the larger groups called systems.
It is important to recognize crystal systems, not only on account of physical properties, but also on account of the difficulty of assigning some crystals to their appropriate class. For example, a crystal consisting of a tetragonal prism and a pinakoid may belong to any one of seven classes. For the time being it is placed in the tetragonal system. When it is carefully investigated and its symmetry determined it may be assigned to the proper class.
Contrary to statements that have been made, we can have, and do have, a two-fold classification in geometrical crystallography—the thirty-two classes based upon symmetry, and the six systems based upon properties that certain classes have in common.
In the opinion of the writer the most satisfactory set of names for the crystal classes is the one based upon names of general forms. These names of Groth are comparatively simple, consistent, and lend themselves to international usage.
- Type
- Research Article
- Information
- Mineralogical magazine and journal of the Mineralogical Society , Volume 25 , Issue 164 , March 1939 , pp. 252 - 258
- Copyright
- Copyright © The Mineralogical Society of Great Britain and Ireland 1939
References
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page 257 note 1 Personal communication, October 1938.
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