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Pyrophyllite is a phyllosilicate mineral composed of aluminium 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 folia have a pronounced pearly lustre, owing to the presence of a perfect cleavage parallel to their surfaces: they are flexible but not elastic, and are usually arranged radially in fan-like or spherical groups. This variety, when heated before the blowpipe, exfoliates and swells up to many times its original volume, hence the name pyrophyllite, from the Greek ''pyros'' (fire) and ''phyllos'' (a leaf),〔 given by R. Hermann in 1829. The color of both varieties is white, pale green, greyish or yellowish; they are very soft (hardness of 1 to 1.5) and are greasy to the touch. The specific gravity is 2.65 - 2.85. The two varieties are thus very similar to talc. ==Occurrence== Pyrophyllite occurs in phyllite and schistose rocks, often associated with kyanite, of which it is an alteration product. It also occurs as hydrothermal deposits. Typical associated minerals include: kyanite, andalusite, topaz, mica and quartz.〔 Deposits containing well-crystallized material are found in:〔 * Manuels, Newfoundland and Labrador, Canada, talc-like bright white appearance, high grade, no impurities; 21 million ton deposit. Currently owned and operated by (Trinity Resources Ltd ). *Russia - pale green foliated masses, very like talc in appearance, are found at Beresovsk near Yekaterinburg in the Urals. *St. Niklas, Zermatt, Valais, Switzerland * at Vaastana, Kristianstad, Sweden * near Ottrje, Ardennes Mountains, Belgium * Ibitiara, Bahia, Brazil * Nagano Prefecture, Japan *It is found near Ogilby, Imperial County at Tres Cerritos, Mariposa County, and the Champion mine, White Mountains, Mono County, California, USA *near Quartzsite, La Paz County, Arizona, USA *the large deposits at the Deep River region of North Carolina, USA *Graves Mountain, Lincoln County, Georgia, USA It is also reported from South Africa where major deposits of pyrophyllite occur within the Ottosdal region, where it is mined for the production of a variety of manufactured goods and blocks are quarried and marketed as "Wonderstone" for the carving of sculptures. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「pyrophyllite」の詳細全文を読む スポンサード リンク
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