Pyrophyllite is composed of aluminium silicate hydroxide: Al2Si4O10(OH)2, is a phyllosilicate class of mineral. It occurs in various forms, viz. crystalline folio and compact masses.
The different uses of pyrophyllite includes
Slate pencils and tailors chalk (French chalk)
Also, carved by the Chinese into small images and ornaments of various kinds.
Other soft compact minerals (steatite and pinite) used for these Chinese carvings are included with pyrophyllite under the terms agalmatolite and pagodite.
Pyrophyllite is easily machineable and has excellent thermal stability. Therefore it is added to clay to reduce thermal expansion when firing but it has many other industry uses when combined with other compounds, such as in insecticide and for making bricks.
Pyrophyllite is also widely used in high-pressure experiments, both as a gasket material and as a pressure-transmitting medium.