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The Mineral pyrophyllite

Golden Brown Pyrophyllite

Pyrophyllite is isomorphous with the common mineral Talc, but has aluminum in place of the magnesium. It is very similar to Talc, with very similar properties and habits. However, it has distinct radiating crystal aggregates which easily identify it. Pyrophyllite is named after the Greek words "pyr" - "fire" and "phyllon" - leaf, regarding its property to exfoliate into fan shapes upon heating.

Chemical Formula

Al2Si4O10(OH)2

Color

White, light green, apple-green, gray, yellow, brown, light blue

Crystal System

Monoclinic

Properties

Streak
White
Hardness
1 - 2
Transparency
Translucent to opaque
Specific Gravity
2.8 - 2.9
Luster
Pearly, dull
Cleavage
1,1
Fracture
Splintery, uneven
Tenacity
Flexible but inelastic
Other ID Marks
1) Has a greasy feel.
2) May fluoresce yellow in longwave ultraviolet light.

Crystal Habits

In dense masses of radiating crystals, often in the shape of interconnected fans. Also in compact veins, and in  radial balls and rosettes. Usually in massive, compact form, with distinct radiating crystals visible.

Additional Information

Composition
Basic aluminum silicate
In Group
Silicates; Phyllosilicates
Striking Features
Distinct crystal habits, light weight, and greasy feel.
Environment
In metamorphic schists and hydrothermal replacement deposits.
Rock Type
Metamorphic

Varieties

 -   Chromium-rich, deep green variety of Pyrophyllite.

Uses

Pyrophyllite is used for ceramics, in paints, insecticides, and in the production of rubber. It is also used as a minor ornamental stone for carvings and sculptures.

Noteworthy Localities

Localities where good Pyrophyllite specimens have come from are limited. Radiating yellow sprays come from Gundagai, New South Wales, Australia; and Monte Folgorito, Pietrasanta, Tuscany, Italy. Light green Pyrophyllite was found in St Niklaus, Zermatt-Saas Fee area, Valais, Switzerland.

In the U.S., North Carolina has produced some of the finest collectible examples of this mineral. Localities include Staley, Randolph Co.; Hillsboro, Orange Co.; the Snow Camp Mine, Alamance Co.; and Cotton Stone Mountain, Troy, Montgomery Co. Dense sprays of large Pyrophyllite crystals have come from Graves Mountain, Lincoln Co., Georgia; and golden-brown interconnected radial sprays associated with Rutile from the Champion Mine, White Mountains, Inyo Co., California.

Common Mineral Associations

Quartz, Chlorite, Hematite, Muscovite, Albite, Rutile, Kyanite, Andalusite, Lazulite

Distingushing Similar Minerals

Talc - Slightly softer, lacks distinct crystal habits of Pyrophyllite. Massive Talc and Pyrophyllite can be very difficult to distinguish.
Wavellite - Greater hardness, different mode of occurrence.

pyrophyllite Photos



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