Pyrophyllite (inclusions in Quartz)
Current inventory:  0 gems
 

  
The name Pyrophyllite comes from the Greek words for fire and leaf, in allusion to its tendency to exfoliate into fan shapes when heated.

Discovered in 1829; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Al₂SiO₄O₁₀(OH)₂

Aluminum Silicate Hydroxide

Molecular Weight:

360.31 gm

Composition:

Aluminum

14.98 %

Al

28.30 %

Al₂O₃

Silicon

31.18 %

Si

66.70 %

SiO₂

Hydrogen

0.56 %

H

5.00 %

H₂O

Oxygen

53.28 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/H.09-10

Nickel-Strunz 10th Ed. ID:

9.EC.10

9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets

Related to:

Pyrophyllite-Talc Group. Polymorphism: 2M1; 1A polytypes.

Members of Group:

Pyrophyllite-Talc Group: Ferripyrophyllite, Minnesotaite, Pyrophyllite, Talc, Willemseite

Varieties:

Cattle Egg Stone, Chrome-Pyrophyllite, Gelpyrophyllite

Synonyms:

Ablikite

Crystal Data

Crystallography:

Monoclinic - Prismatic or Triclinic - Pinacoidal
There are two varieties of Pyrophyllite; one is monoclinic and the other triclinic. Ordinarily they would be treated as two distinct minerals, but their other properties are identical and they are often associated and intergrown.

Crystal Habit:

As lamellar crystals, to 8 cm; in compact spherulitic aggregates of needlelike radiating crystals; as fine grained foliated laminae, granular, massive. 

Twinning:

None

Physical Properties

Cleavage:

Perfect on {001} 

Fracture:

Flexible

Tenacity:

Flexible but inelastic

Moh's Hardness:

1.0 - 2.0

Density:

2.65 - 2.90 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

White, pale blue, yellow, apple-green, grayish green, brownish green; colorless in thin section

Transparency:

Translucent to opaque

Luster:

Pearly to dull

Refractive Index:

1.534 - 1.601  Biaxial ( - )

Birefringence:

0.062

Dispersion:

Weak; r > v

Pleochroism:

n/a

Occurances

Geological Setting:

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

Common Associations:

Kyanite, Andalusite, Topaz, Mica, Quartz

Common Impurities:

n/a

First Recorded Locality:

Pyshminskoe deposit (Staro-Pyshminskoye), Berezovskoe Au Deposit (Berezovsk Mines), Berezovskii (Berezovskii Zavod), Ekaterinburg (Sverdlovsk), Sverdlovskaya Oblast', Middle Urals, Urals Region, Russia

Year Discovered:

1829

View mineral photos:

Pyrophyllite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

The name Pyrophyllite comes from the Greek words for fire and leaf in allusion to its tendency to exfoliate into fan shapes when heated. Pyrophyllite is an unusual mineral with regard to its crystal system; it occurs in two varieties, one is monoclinic and the other triclinic. Ordinarily they would be treated as two distinct minerals, but all of their other properties are identical and they are often associated and intergrown. Pyrophyllite is also an unusual mineral in that it is somewhat flexible, but not elastic. It is a member of the Pyrophyllite-Talc Group of minerals that also includes Talc. Pyrophyllite is identical in physical properties to Talc. The two are isomorphous, meaning they share the same monoclinic structure but have different chemistries.

Pyrophyllite is available as interesting and attractive mineral speciments but never as faceted gems. However, it is available rarely as radiating spray inclusions with pearly luster in clear Quartz cabochons (as pictured above). The main source of these beautiful inclusion cabochons is Minas Gerais, Brazil.

Distribution: Some localities for rich or well-crystallized material follow. In Russia, at Krassik, between Pyschminsk and Beresov, Ural Mountains. From St. Niklas, Zermatt, Valais, Switzerland. In Sweden, at Västanå, Kristianstad. From near Ottré, Ardennes Mountains, Belgium. In the USA, found near Ogilby, Imperial County, at Tres Cerritos, Mariposa County, and the Champion mine, White Mountains, Mono County, California; from near Quartzsite, La Paz County, Arizona; at Staley, Randolph County, Glendon and Robbins, Moore County, and Hillsborough, Orange County, North Carolina; in the Brewer mine, Chesterfield County, South Carolina; on Graves Mountain, Lincoln County, Georgia. From Ibitiara, Bahia, Brazil, in large crystals. In a number of mines in Nagano Prefecture, and elsewhere in Japan.
 

  
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