Pyrophyllite from the Ward Mine, Glendon, Moore County, North Carolina
Pyrophyllite is a phyllosilicate mineral composed of aluminum silicate hydroxide: Al2Si4O10(OH)2. It occurs in two more or less distinct varieties, namely, as crystalline folia and as compact masses; distinct crystals are not known. The compact variety of pyrophyllite is used for slate pencils and tailors chalk (French chalk), and is carved by the Chinese into small images and ornaments of various kinds. Pyrophyllite is easily machinable 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.
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Photo credit: © Phil Degginger / Alamy / Afripics
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Keywords: alsi2o5oh, aluminium, aluminum, carolina, county, crystals, glendon, hydroxide, mineral, minerals, moore, nc, north, phyllosilicate, pyrophyllite, silicate, specimen, specimens, ward
