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A hard, coarse-grain, black-and-white speckled, granite-like igneous rock. Diorite is composed of plagioclase feldspar mixed with hornblende, biotite, and/or augite. Small amounts of orthoclase or quartz may be present. Diorite was valued by the Egyptians and Sumerians for statuary and is presently used in building construction. Sources of diorite include Italy (Sondrio), Germany (Thuringia, Sassonia), Finland, Romania, Sweden, Scotland, and the US (Minnesota).


Synonyms and Related Terms

green stone; trap rock; diorita (Esp.); diorite (Fr.); diorito (Port.); Diorit (Deut.); dioriet (Ned.)

Other Properties

Takes a good polish

Composition C4H8O2
Mohs Hardness 5.5 - 6.0

Additional Images

Sources Checked for Data in Record

  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
  • George Savage, Art and Antique Restorer's Handbook, Rockliff Publishing Corp, London, 1954

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