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External Symmetry of Crystals, 32 Crystal Classes
This site is a lecture by Dr. Stephen Nelson from Tulane University that explores the 32 possible combinations of symmetry operations that define the external symmetry of crystals. The lecture defines the six crystal systems (triclinic, monoclinic, orthorhombic, tetragonal, hexagonal, and isometric) and explains the derivation of the Hermann-Mauguin symbols (also called the international symbols) used to describe the crystal classes from the symmetry content. Tables and illustrations accompany the text.
Intended for grade levels:
  • College (15-16)
Type of resource:
  • Visual:
    • Illustration - scientific
  • Text:
    • Ref. material
  • Geological Sciences:
    • Geochemistry
    • Mineralogy or petrology
Technical requirements:
No specific technical requirements, just a browser required
Cost / Copyright:
No cost
Copyright 2001 Tulane University New Orleans, LA 70118
DLESE Catalog ID: SERC-NAGT-000-000-000-727
Resource contact / Creator / Publisher:
Author: Stephen A. Nelson
Tulane University