pyrophylliit

Pyrophyllite is a phyllosilicate mineral belonging to the kaolinite-aluminium silicate group. It is characterized by a soft, talc-like feel, and typically appears in shades of white, gray, green, or brown. Pyrophyllite generally forms in foliated masses, and its structure consists of sheet-like layers of aluminium silicate.

This mineral commonly occurs in metamorphic rocks, particularly in regions where aluminous sediments have undergone hydrothermal alteration or low-grade metamorphism. It is often associated with other clay minerals such as talc, chlorite, and kaolinite.

Pyrophyllite's physical properties include a hardness of 1 to 2 on the Mohs scale, making it one of the softer minerals; it has a greasy or pearly luster and a perfect basal cleavage. Its streak is typically white or colorless. Pyrophyllite is non-toxic, chemically inert, and exhibits good thermal stability.

The primary industrial uses of pyrophyllite include the manufacture of ceramics, refractories, and insulating materials, due to its high heat resistance and insulating properties. It is also used as a filler and extender in paints, plastics, and rubber industries. Additionally, pyrophyllite is employed in the production of low-temperature fired ceramic bodies and as a raw material in the synthesis of certain aluminosilicate compounds.

Mineralogically, pyrophyllite has the chemical formula Al₂Si₄O₁₀(OH)₂. It is distinguished from talc primarily by its chemical composition and crystal structure, despite their similar physical appearances. Its occurrence and properties make it an important mineral in both geological and industrial contexts.