Prase

Prase is a leek-green (Greek - prason) Quartz aggregate, usually classified as a Chalcedony, whose colour is caused by chlorite inclusions.
General Information
A variety or type of:Quartz
Chemical Formula
SiO
 
2
Michael O’Donoghue, Gems, Sixth Edition (2006)
Photos of natural/un-cut material from mindat.org
Physical Properties of Prase
Mohs Hardness7
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Specific Gravity2.64 to 2.69
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Cleavage QualityNone
Arthur Thomas, Gemstones (2009)
FractureConchoidal
Michael O’Donoghue, Gems, Sixth Edition (2006)
Optical Properties of Prase
Refractive Index1.544 to 1.553
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Optical CharacterUniaxial/+
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Birefringence0.009
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Colour
Colour (General)Grayish green color due actinolite fibers, blue color due to crocidolite fibers
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Causes of ColourChlorite inclusions
Walter Schumann, Gemstones of the world (2001)
TransparencyTransparent,Translucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
LustreVitreous
Arthur Thomas, Gemstones (2009)
Crystallography of Prase
Crystal SystemTrigonal
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
HabitPrismatic
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Prase information at mindat.org
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