Pyrophyllite

Aluminum Silicate Hydroxide
AlSi₂O₅OH

Pyrophyllite finds the same use as talc, that is why most of the countries combine the production figures of talc, steatite, etc. and pyrophyllite together.

The History Says

Pyrophyllite gets its name from the Greek words for fire and leaf as in "fire-leaf". Phyllite is named after the Greek word for leaf as well, in allusion to its flaky fracture. But pyrophyllite gets its name from the fact that it exfoliates when water is driven off upon heating, leaving a flaky mass. The flakes are actually the silicate sheets that are a testament to pyrophyllite's structure.

The Present Scenario

There are actually two pyrophyllite minerals. One is monoclinic and the other triclinic. Ordinarily they would be treated as two distinct minerals, but their properties are identical and they are often associated and intergrown. Separating them serves no purpose and the two minerals are often considered as one; at least for now.

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PYROPHYLLITE is a secondary mineral of composition Al₂O₃.4SiO₂.H₂O, containing 28.3% Al₂O₃, 66.7% SiO₂ and 5% H₂O. In appearance it looks like talc and in physical properties also it is identical to talc. However, it differs in chemical composition, as talc is a hydrous magnesium silicate whereas pyrophyllite is hydrous aluminium silicate.

It is identified in hand specimen by imperfect micaceous structure. It is opaque to translucent in thin section, appears to consist of extremely fine grained talc and kaolinite. It is a little harder than talc. Its sp. gr. is 2.8 to 2.9.

Pyrophyllite finds the same use as talc, that is why most of the countries combine the production figures of talc, steatite, etc. and pyrophyllite together. It would be proper to report separately the production figures of these two minerals.

Hardness	Associated Minerals	Fracture	Colour	characteristics	Luster	Field Indicators
1 - 1.5 (soft enough to be scratched by a fingernail).	micas sericite chlorite graphite quartz albite barite gypsum andalusite kyanite sillimanite lazulite epidote	uneven or splintery	usually white, colorless, gray, yellow, pale green and/or blue. It can also be stained brown by iron oxides	Cleavage sheets are flexible, but inelastic. A distinctive greasy feel to the touch	greasy to dull, but pearly on cleavage surfaces	crystal habit, color, cleavage, softness, aluminum test and feel.

World Resources

Many countries do not report the production of pyrophyllite separately. It is included with talc. Thus, much useful information on its occurrence, research, utilization and production has remained obscure. Production, as far as known, has been reported from Canada, Republic of Korea, the Rep. of South Africa and the USA.

Other occurrences in North Carolina are in Granville, Orange, Alamance and Montgomery counties. Occurrences have also been noted in Newfoundland, Nova Scotia, Vancouver island, South Mountain, and in California. At present, the production comes mainly from Moore county, North Carolina and San Diego county, California.

The pyrophyllite deposits of the USA are associated with tuffaceous rocks which exhibit various stages of alteration. They are found to occur as narrow bands or zones aligned with the cleavage, strike and dip of the country rock.

Notable Occurrences

• Randolph
• Guilford and Orange Counties
• North Carolina
• Chesterfield County
• South Carolina
• Mariposa County and San Bernardino County
• California
• Arizona and Graves Mountain
• Georgia
• USA as well as Belgium
• China
• Switzerland
• Mexico
• Minas Gerais
• Brazil
• Sweden
• Ural Mountains
• Russia
• Korea
• Japan