Realgar

Big Photo

China
7.46 carats
© Rarestone.com

Realgar is named from Arabic "rahj al-gar" - powder of the mine, because it was found in a silver mine.

Realgar forms red to orange-yellow prismatic crystals or granular masses. The crystals disintegrate to a powder after long exposure to light. However, this process takes a very long time. Realgar specimens should be kept in the dark, in an eclosed container.

Realgar is a very rare gem. It is very soft and somewhat unstable.

Realgar Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
General Information
Chemical Formula
AsS
Michael O’Donoghue, Gems, Sixth Edition (2006)
Photos of natural/un-cut material from mindat.org
Physical Properties of Realgar
Mohs Hardness1.5 to 2
Michael O’Donoghue, Gems, Sixth Edition (2006)
Specific Gravity3.56
Michael O’Donoghue, Gems, Sixth Edition (2006)
TenacityBrittle,Sectile
Anthony et al, Handbook of mineralogy (2001) Sectile, also slightly brittle
Cleavage QualityGood
Anthony et al, Handbook of mineralogy (2001)
Light SensitivityDisintegrate to a powder after long exposure to light
Michael O’Donoghue, Gems, Sixth Edition (2006)
Optical Properties of Realgar
Refractive Index2.538 to 2.704
Michael O’Donoghue, Gems, Sixth Edition (2006) RI for the alpha, beta and gamma rays is 2.538, 2.684 and 2.704
Optical CharacterBiaxial/-
Michael O’Donoghue, Gems, Sixth Edition (2006)
Birefringence0.166
Michael O’Donoghue, Gems, Sixth Edition (2006)
PleochroismNearly colorless to pale golden yellow
Anthony et al, Handbook of mineralogy (2001)
DispersionVery strong
Anthony et al, Handbook of mineralogy (2001)
Colour
Colour (General)Red to orange-yellow
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
TransparencyTransparent
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
LustreGreasy
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Crystallography of Realgar
Crystal SystemMonoclinic
Michael O’Donoghue, Gems, Sixth Edition (2006)
HabitPrismatic
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Geological Environment
Where found:Most commonly as a low-temperature hydrothermal vein mineral associated with As–Sb minerals; also as volcanic sublimations and in hot spring deposits; in carbonate and clay.
sedimentary rocks
Anthony et al, Handbook of mineralogy (2001)
Further Information
Mineral information:Realgar information at mindat.org
Significant Gem Localities
Peru
 
  • Huancavelica Department
    • Castrovirreyna Province
USA
 
  • Nevada
    • Humboldt Co.
      • Osgood Mts
        • Potosi District
          • Adam Peak
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 442
  • Washington
    • King Co.
      • Franklin
        • Green River Gorge
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 442
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 442
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