Marcasite

The name Marcasite is derived from Arabic word for pyrite. Marcasite and pyrite are polymorphs. Marcasite is lighter and more brittle than pyrite.

Marcasite forms metallic pale brass-yellow coloured, tabular or pyramidal, sometimes stalactic or globular crystals. On fresh surfaces it is pale yellow to almost white and has a bright metallic lustre.
General Information
Chemical Formula
FeS
 
2
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Photos of natural/un-cut material from mindat.org
Physical Properties of Marcasite
Mohs Hardness6 to 6.5
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Specific Gravity4.80 to 4.90
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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TenacityBrittle
Arthur Thomas, Gemstones (2009)
Cleavage QualityPoor
Arthur Thomas, Gemstones (2009)
FractureUneven
Arthur Thomas, Gemstones (2009)
Optical Properties of Marcasite
Refractive IndexNil
Arthur Thomas, Gemstones (2009)
BirefringenceNil
Arthur Thomas, Gemstones (2009)
PleochroismNil
Arthur Thomas, Gemstones (2009)
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DispersionNil
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)Yellow, bronze colour
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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TransparencyOpaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreMetallic
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Crystallography of Marcasite
Crystal SystemOrthorhombic
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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HabitTypically tabular but may be pyramidal
or prismatic and may show curved faces
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Geological Environment
Where found:Marcasite occurs in sedimentary environments formed characteristically under low temperature, highly acidic conditions.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Marcasite information at mindat.org
Significant Gem Localities
Myanmar
 
  • Mandalay Region
    • Pyin-Oo-Lwin District
      • Mogok Township
        • Marble Ark
Ted Themelis (2008) Gems & mines of Mogok
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