Chiastolite

Chiastolite is an opaque variety of Andalusite. When the crystal is cut through, its cross-section will usually show an off-white body colour and a blackish diagonal cross, caused by carbonaceous inclusions. These crystals are often sectioned, polished and used as amulets, sometimes chiastolite is cut into cabochons.
General Information
A variety or type of:Andalusite
Chemical Formula
Al
 
2
SiO
 
5
Michael O’Donoghue, Gems, Sixth edition (2006)
Photos of natural/un-cut material from mindat.org
Chiastolite Simulants
Do not exist due to its distinct marking. - Gemstones of the world, Walter Schumann, 2001, p 178
Physical Properties of Chiastolite
Mohs Hardness5 to 5.5
Walter Schumann, Gemstones of the world (2001)
Specific Gravity3.00 to 3.15
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Cleavage QualityDistinct
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Optical Properties of Chiastolite
Refractive Index1.627 to 1.645
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Optical CharacterBiaxial/-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Birefringence0.007 to 0.013
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Colour
Colour (General)White, gray, yellowish
Walter Schumann, Gemstones of the world (2001)
More from other references
TransparencyTranslucent,Opaque
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
LustreVitreous
Arthur Thomas, Gemstones (2009)
Crystallography of Chiastolite
Crystal SystemOrthorhombic
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
HabitSquare prisms
Arthur Thomas, Gemstones (2009)
Further Information
Mineral information:Chiastolite information at mindat.org
Significant Gem Localities
Australia
 
  • South Australia
    • Olary Province
      • Kalabity homestead area
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 381
USA
 
  • California
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 382
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