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Article: Marcasite


General Information and Physical Properties of Marcasite

  • Marcasite is a sulfide mineral with the chemical formula FeS.
  • It has an orthorhombic crystal structure and belongs to the Strunz classification 2.EB.10a.
  • The crystal habit of marcasite is typically tabular on {010}, with curved faces common.
  • It exhibits cleavage on {101} and {110} planes.
  • Marcasite has a metallic luster and a dark-grey to black streak.
  • Crystalline structure
  • Metallic luster
  • Hardness of 6 to 6.5 on Mohs scale
  • Brittle nature
  • Pale yellow to bronze color

Occurrence of Marcasite

  • Marcasite can be formed as both a primary and a secondary mineral.
  • It is commonly found in sedimentary rocks such as shales, limestones, and low-grade coals.
  • It also occurs in low-temperature hydrothermal veins.
  • Associated minerals include pyrite, pyrrhotite, galena, sphalerite, fluorite, dolomite, and calcite.
  • In sedimentary rocks, marcasite can form nodules, concretions, and crystals.
  • Found in sedimentary rocks
  • Commonly associated with coal deposits
  • Occurs in hydrothermal veins
  • Found in organic-rich environments
  • Often found in shale and limestone

Uses and Applications of Marcasite

  • Jewelry and decorative purposes
  • Industrial applications as a catalyst
  • Historical use as a substitute for pyrite
  • Used in traditional medicine for its healing properties
  • Utilized in the production of sulfuric acid

Formation and Decay of Marcasite

  • Forms through the process of hydrothermal activity
  • Occurs in low-temperature environments
  • Result of the reaction between iron and sulfur
  • Precipitates from groundwater solutions
  • Forms in voids and fractures within rocks
  • Marcasite reacts more readily than pyrite under conditions of high humidity.
  • The disintegration of marcasite results in the formation of iron(II) sulfate and sulfuric acid.
  • The product of marcasite decay is a white powder called melanterite.
  • This decay process can damage other sulfide minerals and mineral labels.
  • Storage conditions with low humidity can prevent or slow down marcasite decay.

Comparison between Marcasite and Pyrite

  • Marcasite has a lower hardness compared to pyrite.
  • Marcasite is more brittle and prone to decay.
  • Pyrite has a golden-yellow color, while marcasite is paler.
  • Marcasite is less common than pyrite in nature.
  • Pyrite is more stable and less likely to oxidize than marcasite.

Marcasite Data Sources

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