Pyrophyllite is a mineral species belonging to the clay family and composed of hydrous aluminium silicate HAl (SiOf)₂. It occurs in two more or less distinct varieties, namely, as crystalline folia and as compact masses; distinct crystals are not known. Minerals are natural compounds formed through geological processes. ... Clay is a generic term for an aggregate of hydrous silicate particles less than 4 μm (micrometres) in diameter. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13 (IIIA), 3, p Density, Hardness 2700 kg/m3, 2. ... In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ...

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 irip (fire) and ??? (a leaf), given by R. Hermann in 1829. The color of both varieties is white, pale green, greyish or yellowish; they are very soft (H. = 12) and are greasy to the touch. The specific gravity is 2.82.9. The two varieties are thus very similar respectively to talc (q.v.) and it silicate. 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 (steatite and pinite) used for these Chinese carvings are included with pyrophyllite under the terms agalmatolite and pagodite. Talc block Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2. ...

Pyrophyllite occurs in schistose rocks, often associated with cyanite, of which it is an alteration product. Pale green foliated masses, very like talc in appearance, are found at Beresovsk near Ekaterinburg in the Urals, and at Zermatt in Switzerland. The most extensive deposits are in the Deep River region of North Carolina, where the compact variety is mined, and in South Carolina and Georgia. Cyanite ia a native aluminium silicate mineral, AlSiOi, crystallizing in the anorthic system. ... Photograph of snow-covered Yekaterinburg Yekaterinburgs Church on the Blood, built on the spot where the Tsar and his family were murdered. ... The Ural Mountains, (Russian: Ура́льские го́ры = Ура́л) also known simply as the Urals, are a mountain range that run roughly north and south through western Russia. ... In June, the Matterhorn is still snow-covered, while it is spring in Zermatt below. ... The Deep River, shown highlighted The Deep River is a tributary of the Cape Fear River, approximately 125 mi (201 km) long, in north central North Carolina in the United States. ... State nickname: Tar Heel State Other U.S. States Capital Raleigh Largest city Charlotte Governor Michael Easley Official languages English Area 139,509 km² (28th)  - Land 126,256 km²  - Water 13,227 km² (9. ... State nickname: Palmetto State Other U.S. States Capital Columbia Largest city Columbia Governor Mark Sanford Official languages English Area 82,965 km² (40th)  - Land 78,051 km²  - Water 4,915 km² (6%) Population (2000)  - Population 4,012,012 (26th)  - Density 51. ...

This article incorporates text from the public domain 1911 Encyclopædia Britannica. The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ... The Eleventh Edition of the Encyclopædia Britannica ( 1911) in many ways represents the sum of knowledge at the beginning of the 20th century. ...