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Phlogopite thin section

A magnesium Mica mineral that is usually a yellowish brown but may sometimes be reddish brown. Phlogopite is a transparent to translucent stone that is mined in Romania, Switzerland, Italy, Finland, Sweden, the Malagasy Republic, Canada (Ontario, Quebec) and the United States (New York, New Jersey, California). It is usually found in marbles. Phlogopite is primarily used as an electrical insulator.

Synonyms and Related Terms

brown mica; flogopita (Esp.); flogopit (Pol.); flogopite (Port.); Phlogopit (Deut.); flogopiet (Ned.)



Physical and Chemical Properties

  • Monoclinic system with prismatic crystals.
  • Cleavage is basal forming thin elastic sheets.
  • Fracture = flaky.
  • Luster = pearly to adamantine.
  • Streak = colorless.
Composition K(Mg,Fe)3AlSi3O10(OH)2
Mohs Hardness 2.5 - 3.0
Density 2.78-2.85 g/ml

Resources and Citations

  • Mineralogy Database: Phlogopite
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 505
  • 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
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998

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