Pyrophyllite is a phyllosilicate
mineralspecies belonging to the clayfamily and composed of aluminium silicate hydroxide: AlSi2O5OH. 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. Hermannin 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 gravityis 2.65 - 2.85. The two varieties are thus very similar to talc. 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. Other soft compact minerals ( steatiteand pinite) used for these Chinese carvings are included with pyrophyllite under the terms agalmatolite and pagodite.
Pyrophyllite occurs in
phylliteand schistose rocks, often associated with kyanite, of which it is an alteration product. Pale green foliated masses, very like talc in appearance, are found at Beresovsknear Yekaterinburgin the Urals, and at Zermattin Switzerland. The most extensive deposits are in the Deep River region of North Carolina, where the compact variety is mined, and in South Carolinaand Georgia. Major deposits of pyrophyllite occur within region of Ottosdal, South Africa, 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. In Australia, pyrophyllite has been mined at three sites near Pambula on the Sapphire Coast of NSW.
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.
* [http://mineral.galleries.com/minerals/silicate/pyrophyl/pyrophyl.htm Mineral galleries]
* [http://webmineral.com/data/Pyrophyllite.shtml Webmineral]
* [http://minerals.usgs.gov/minerals/pubs/commodity/talc/ USGS]
* [http://www.psranawat.org/non_mettalic/pyrophylite.htm Industrial specifications]
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PYROPHYLLITE — Très semblable au talc, la pyrophyllite est un phyllosilicate d’alumine, de formule chimique: Al2(Si410)(OH)2, ou Al23, 4 Si2, H2O. Elle possède une certaine aptitude à se débiter en feuillets, d’où l’origine de son nom (de deux mots grecs: pyros … Encyclopédie Universelle
Pyrophyllite — Py*roph yl*lite, n. [Pyro + Gr. ? leaf.] (Min.) A mineral, usually of a white or greenish color and pearly luster, consisting chiefly of the hydrous silicate of alumina. [1913 Webster] … The Collaborative International Dictionary of English
pyrophyllite — [pī΄rə fil′īt΄] n. [Ger pyrophyllit: see PYRO & PHYLL(O) & ITE1] a very soft, greasy, monoclinic mineral, AlSi2O5 (OH), that is similar to talc in structure, used as a lubricant and in making rubber, soap, etc.; hydrous aluminum silicate … English World dictionary
pyrophyllite — /puy reuh fil uyt, puy rof euh luyt /, n. Mineral. a phyllosilicate, AlSi2O5(OH), usually having a white or greenish color, and occurring in either foliated or compact masses, the latter variety being used like soapstone. [1820 30; < G… … Universalium
pyrophyllite — noun a white or greenish aluminum silicate mineral (resembles talc) • Hypernyms: ↑mineral * * * ˌpīrōˈfiˌlīt, pīˈräfəˌl noun ( s) Etymology: German pyrophyllit, from pyr + phyll + it ite : a mineral AlSi2O5(OH) that is … Useful english dictionary
Pyrophyllite — Ressemblant au talc, la pyrophyllite est un phyllosilicate d alumine. Sa formule chimique est la suivante : Al2(Si4O10)(OH)2, ou Al2O3, 4 SiO2, H2O. Elle possède une certaine aptitude à être en feuillets. L origine de son nom se décompose de … Wikipédia en Français
pyrophyllite — pirofilitas statusas T sritis chemija apibrėžtis Mineralas. formulė Al₂[(OH)₂|Si₄O₁₀] atitikmenys: angl. pyrophyllite rus. пирофиллит … Chemijos terminų aiškinamasis žodynas
pyrophyllite — noun Etymology: German Pyrophyllit, from Greek pyr + phyllon leaf more at blade Date: 1830 a soft usually white or greenish mineral that is a hydrous aluminum silicate, resembles talc, occurs in a foliated form or in compact masses, and is used… … New Collegiate Dictionary
pyrophyllite — noun A soft, pale aluminosilicate mineral, somewhat resembling talc … Wiktionary
pyrophyllite — (pi ro fil li t ) s. f. Silicate d alumine et de magnésie qui s exfolie sous l action du feu. ÉTYMOLOGIE Pyro..., et, feuille … Dictionnaire de la Langue Française d'Émile Littré