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A calcium-rich plagioclase feldspar mineral composed of calcium aluminosilicate. Anorthite occurs as brittle, translucent, white ,or gray crystals. It is found in many igneous rocks such as Gabbro and Granite. Major deposits occur in Italy (Trentino, the lavas of Vesuvius, and Monte Somma), Finland, Sweden (Södermanland), India (Tamil Nadu), Japan (Miyake), and the United States (New Jersey).


Anorthite PMA.TIF

Raman (RASMIN)


Synonyms and Related Terms

calcium feldspar; Anorthit (Deut.); anorthiet (Ned.); anortyt (Pol); anortita (Esp.); anortite (Port.); anortyt (Ned.)

Physical and Chemical Properties

  • Crystalline system = triclinic
  • Cleavage = perfect in one direction
  • Pleochroism = yellow to dark green to transparent to opaque
  • Luster = vitreous
Composition CaAl2Si2O8
Mohs Hardness 6.0-6.5
Density 2.74-2.76 g/ml
Refractive Index 1.51

Resources and Citations

  • Robert Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Company, Radnor, PA, 1992
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: density=2.74-2.76