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Pyrophyllite
Current inventory:  0 gems
 

Chemistry:  Al₂Si₄O₁₀(OH)₂

Discovered in 1829;   IMA status: Valid (pre-IMA; Grandfathered).
The name Pyrophyllite comes from the Greek words for fire and leaf, in allusion to its tendency to exfoliate into fan shapes when heated.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/H.09-10

8 : Silicates
H : Phyllosilicates (layered), Tetragonal or pseudotetragonal layered structures [Si4O10]4- and others
09 : Talc series

Crystal Data

Crystallography:

Triclinic - Pinacoidal or Monoclinic - Prismatic

Crystal Habit:

As lamellar crystals, to 8 cm; in compact spherulitic aggregates of needlelike radiating crystals; as fine grained foliated laminae, granular, massive. Earthy - Dull, clay-like texture with no visible crystalline affinities.

Twinning:

None

Physical Properties

Cleavage:

[001] Perfect

Fracture:

Flexible fragments, inelastic

Tenacity:

Brittle

Moh's Hardness:

1.5 - 2.0

Density:

2.65 - 2.90 (g/cm³)

Luminescence:

Fluorescent

Radioactivity:

Not Radioactive

Optical Properties

Color:

Brown green, Brownish yellow, Greenish, Gray green, Gray white

Transparency:

Translucent to Opaque

Luster:

Pearly

Refractive Index:

1.534 - 1.601  Biaxial ( - )

Birefringence:

0.0450 - 0.0620

Dispersion:

None

Pleochroism:

X = colorless
Y = colorless
Z = colorless

Occurances

Geological Setting:

Somewhat uncommon, found both in hydrothermal veins and in bedded deposits in schistose metamorphic rocks.

Type Locality:

Staro-Pyshimskoye Mine, Berezovskoye Au Deposit (Berezovsk Mines), Berezovskii (Berezovskii Zavod), Ekaterinburg (Yekaterinburg; Sverdlovsk), Sverdlovskaya Oblast', Urals Region, Russia

Year Discovered:

1829

View mineral photos:

Pyrophyllite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Pyrophyllite is an unusual mineral in that it is somewhat flexible, but not elastic. It is very soft, with a Moh's hardness of only 1.5 - 2.0. It is a member of the Talc mineral series and some forms of the mineral are clay-like. It occurs in two more or less distinct varieties, namely, as crystalline folia and as compact masses; distinct crystals are not known. The greenish material contrasted by the tan clay-like matrix material makes for unusual and beautiful cabochons. Pyrophyllite comes from a number of locations worldwide, most notably Beresovsk near Ekaterinburg in the Urals, Russia; Zermatt, Switzerland; Deep River region of North Carolina, USA; Ottosdal region, South Africa; and Yunan, China.
 

  
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