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Meaning of marcasite

mar•ca•site

Pronunciation: (mär'ku-sīt"), [key]
— n.
  1. a common mineral, iron disulfide, FeS, chemically similar to pyrite but crystallizing in the orthorhombic system.
  2. any of the crystallized forms of iron pyrites, much used in the 18th century for ornaments.
  3. a specimen or ornament of this substance.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.