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Diopside green prismatic crystal; Image credit: Didier Descouens

A green, calcium magnesium silicate mineral sometimes used as a Gemstone. Diopside is a Pyroxene type mineral with short, monoclinic crystals. The transparent to translucent crystals have either a square or octagonal cross section. The color of diopside crystals usually from light to dark green, but may be blue, brown, colorless or pale violet. Diopside has been found at many locations throughout Europe (Russia, Finland, Sweden, Switzerland and Italy), Canada (Ontario, Quebec) and the United States (New York, California and Maine). Powdered diopside is used as a matting agent in ceramic glazes.

Synonyms and Related Terms

calcium magnesium silicate; diopside (Fr.); diópsido (Esp., Port.); Diposid (Deut.); diopsiet (Ned.)



Raman (U of Parma)


Physical and Chemical Properties

  • Monoclinic system with slender square or octagonal prisms that are often twinned
  • Cleavage occurs at intersecting angles of 87 and 93 degrees
  • Fracture = uneven to conchoidal
  • Luster = vitreous to dull
  • Streak = white, gray or green
  • Fluorescence = green in LW; inert in SW
  • Pleochroism = weak to strong; light and dark green
  • Dispersion = weak to distinct
Composition CaMgSi2O6
Mohs Hardness 5.5 - 6.5
Density 3.2-3.6 g/ml
Refractive Index 1.66-1.73
Birefringence 0.024 - 0.030

Resources and Citations

  • Mineralogy Database: Diopside
  • Gem Identification Lab Manual, Gemological Institute of America, 2016.
  • Robert Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Company, Radnor, PA, 1992
  • Encyclopedia Britannica, http://www.britannica.com Comment: "diopside" [Accessed December 4, 2001]. (tech info)
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
  • Wikipedia: Diopside (Accessed Sept. 7, 2005 and Dec 2022)
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998