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Pyrophyllite

Phyllosilicate - Monoclinic - not a Mica group member but is a member of the Talc series. Talc is found as tabular crystals {001}. foliated and stellate masses, inelastic laminae, less abundant than Talc. Forms from the alteration of Feldspars, in Al-rich rocks, under acidic conditions >300 d C...below which Kaolinite forms.
- Formula
- Al2Si4O10(OH)2
- Crystal System
- Triclinic
- Crystal Habit
- Earthy
- Cleavage
- Perfect, None, None
- Luster
- Pearly
- Color
- brown green, brownish yellow, greenish, gray green, gray white
- Streak
- white
- Class
- Triclinic - Pinacoidal
- Fracture
- Flexible
- Hardness
- 1.5-2
- WebMineral
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- Mindat
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Pyrophyllite from Indian Gulch, Mariposa Co., California, United States

Phyllosilicate - Monoclinic - not a Mica group member but is a member of the Talc series. Talc is found as tabular crystals {001}. foliated and stellate masses, inelastic laminae, less abundant than Talc. Forms from the alteration of Feldspars, in Al-rich rocks, under acidic conditions >300 d C...below which Kaolinite forms.
Pyrophyllite from Graves Mountain, Lincoln Co., Georgia, United States

Stellate groups of soft Pyrophyllite crystals in patterns 1.5cm across.