Pyrophyllite

Pyrophyllite is named from Greek pyr - fire, plus phyllon - a leaf, alluding to its exfoliation when strongly heated.

Pyrophyllite forms white, pale blue, yellow, green, brown, translucent or opaque, compact spherulitic aggregates of acicular radiating crystals or foliated laminae.

Pyrophyllite is used for ornamental carvings. The similarity to Soapstone increases ornamental interest in pyrophyllite.
General Information
Chemical Formula
Al
 
2
Si
 
4
O
 
10
(OH)
 
2
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Photos of natural/un-cut material from mindat.org
Physical Properties of Pyrophyllite
Mohs Hardness1 to 2
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Specific Gravity2.65 to 2.90
Michael O’Donoghue, Gems, Sixth Edition (2006)
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TenacityFlexible
Anthony et al, Handbook of mineralogy (2001) Flexible but inelastic
Cleavage QualityPerfect
Michael O’Donoghue, Gems, Sixth Edition (2006)
FractureSplintery
Arthur Thomas, Gemstones (2009)
Optical Properties of Pyrophyllite
Refractive Index1.534 to 1.601
Michael O’Donoghue, Gems, Sixth Edition (2006) RI for the alpha, beta and gamma rays is 1.534–1.556, 1.586–1.589, 1.596–1.601More from other references
Optical CharacterBiaxial/-
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Birefringence0.050
Michael O’Donoghue, Gems, Sixth Edition (2006)
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PleochroismNil
Arthur Thomas, Gemstones (2009)
DispersionNil
Arthur Thomas, Gemstones (2009)
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Colour
Colour (General)White or pale shades of blue, yellow or green
Michael O’Donoghue, Gems, Sixth Edition (2006)
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TransparencyTranslucent,Opaque
Michael O’Donoghue, Gems, Sixth Edition (2006)
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LustrePearly,Greasy
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Crystallography of Pyrophyllite
Crystal SystemMonoclinic,Triclinic
Michael O’Donoghue, Gems, Sixth Edition (2006)
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HabitSpherulitic aggregates of acicular radiating crystals or foliated laminae
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Geological Environment
Where found:Pyrophyllite occurs in hydrothermal veins and in deposits of schistose rocks.
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Further Information
Mineral information:Pyrophyllite information at mindat.org
Significant Gem Localities
Brazil
 
  • Bahia
    • Ibitiara
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 441
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