Hercynite

Hercynite is named after Silva Hercynia, the Latin name for the Bohemian Forest, where the mineral was discovered.

Hercynite is a mineral of spinel group. It forms dark blue-green, yellow, brown crystals with vitreous lustre.
General Information
Chemical Formula
Fe
2+
 
Al
 
2
O
 
4
Gemdat.org, Management Team (2012)
Photos of natural/un-cut material from mindat.org
Physical Properties of Hercynite
Mohs Hardness7.5 to 8
Anthony et al, Handbook of mineralogy (2001)
Specific Gravity4.39
Gemdat.org, Management Team (2012) CalculatedMore from other references
TenacityBrittle
Gemdat.org, Management Team (2012)
FractureConchoidal
Gemdat.org, Management Team (2012)
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Optical Properties of Hercynite
Refractive Index1.80 to 1.83
Anthony et al, Handbook of mineralogy (2001)
Optical CharacterIsotropic
Anthony et al, Handbook of mineralogy (2001)
Colour
Colour (General)Dark blue-green, yellow, brown
Gemdat.org, Management Team (2012)
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TransparencyTranslucent,Opaque
Anthony et al, Handbook of mineralogy (2001) Translucent through thin edges.
LustreVitreous
Anthony et al, Handbook of mineralogy (2001)
Crystallography of Hercynite
Crystal SystemIsometric
Gemdat.org, Management Team (2012)
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HabitCrystals usually octahedral
Gemdat.org, Management Team (2012)
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Geological Environment
Where found:In high-grade metamorphosed ferruginous argillaceous sediments and in some mafic and ultramafic igneous rocks. Also in placers.
Anthony et al, Handbook of mineralogy (2001)
Further Information
Mineral information:Hercynite information at mindat.org
Significant Gem Localities
Kyrgyzstan
 
  • Naryn Region
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