Pyrophyllite is a
phyllosilicate
Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust.
In mineralogy, silica (silicon dioxide, ) is usually consid ...
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
composed of
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
silicate hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...
: Al
2Si
4O
10(OH)
2. It occurs in two forms (
habit
A habit (or wont as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously. s): crystalline folia and compact masses; distinct
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
s are not known.
The folia have a pronounced pearly
luster, 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 , exfoliates and swells up to many times its original volume, hence the name pyrophyllite, from the Greek ''pyro-'' (πυρο-, the combining form of πῦρ fire) and ''phyllos'' (a leaf),
[ given by ]R. Hermann
R. or r. may refer to:
* ''Reign'', the period of time during which an Emperor, king, queen, etc., is ruler.
* '' Rex'', abbreviated as R., the Latin word meaning King
* ''Regina'', abbreviated as R., the Latin word meaning Queen
* or , abbreviat ...
in 1829. The color of both varieties is white, pale green, greyish or yellowish; they are very soft (hardness
In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
of 1.0 to 1.5) and are greasy to the touch. The specific gravity
Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest ...
is 2.65 - 2.85. The two varieties are thus very similar to talc
Talc, or talcum, is a clay mineral, composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent a ...
.
Occurrence
Pyrophyllite occurs in phyllite
Phyllite ( ) is a type of foliated metamorphic rock created from slate that is further metamorphosed so that very fine grained white mica achieves a preferred orientation.Stephen Marshak ''Essentials of Geology'', 3rd ed. It is primarily compo ...
and schist
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes ...
ose rocks, often associated with kyanite
Kyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure polymorph of andalusite and sillimanite, and the presence of kyanite in metamorphic rocks gener ...
, of which it is an alteration product. It also occurs as hydrothermal
Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...
deposits. Typical associated minerals include: kyanite, andalusite
Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5. This mineral was called andalousite by Delamétehrie, who thought it came from Andalusia, Spain. It soon became clear that it was a locality error, and that the spe ...
, topaz, mica and quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
.[
Deposits containing well-crystallized material are found in:][
* Manuels, ]Newfoundland and Labrador
Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost provinces and territories of Canada, province of Canada, in the country's Atlantic Canada, Atlantic region. The province comprises t ...
, Canada, talc-like bright white appearance, high grade, no impurities; 21 million ton deposit. Currently 2 square miles owned and operated b
Trinity Resources Ltd
and the surrounding 20 km2 including the Dog Pond and Trout Pond owned by White Fox Silver Resources Inc.
*Russia - pale green foliated masses, very like talc in appearance, are found at Beresovsk near Yekaterinburg
Yekaterinburg ( ; rus, Екатеринбург, p=jɪkətʲɪrʲɪnˈburk), alternatively romanized as Ekaterinburg and formerly known as Sverdlovsk ( rus, Свердло́вск, , svʲɪrˈdlofsk, 1924–1991), is a city and the administra ...
in the Ural
Ural may refer to:
*Ural (region), in Russia and Kazakhstan
*Ural Mountains, in Russia and Kazakhstan
*Ural (river), in Russia and Kazakhstan
* Ual (tool), a mortar tool used by the Bodo people of India
*Ural Federal District, in Russia
*Ural econ ...
s.
* St. Niklas, Zermatt
Zermatt () is a municipality in the district of Visp in the German-speaking section of the canton of Valais in Switzerland. It has a year-round population of about 5,800 and is classified as a town by the Swiss Federal Statistical Office (FSO) ...
, Valais
Valais ( , , ; frp, Valês; german: Wallis ), more formally the Canton of Valais,; german: Kanton Wallis; in other official Swiss languages outside Valais: it, (Canton) Vallese ; rm, (Chantun) Vallais. is one of the 26 cantons forming the S ...
, Switzerland
* Vaastana, Kristianstad
Kristianstad (, ; older spelling from Danish ''Christianstad'') is a city and the seat of Kristianstad Municipality, Scania County, Sweden with 40,145 inhabitants in 2016. During the last 15 years, it has gone from a garrison town to a devel ...
, Sweden
* Near Ottrje, Ardennes Mountains
The Ardennes (french: Ardenne ; nl, Ardennen ; german: Ardennen; wa, Årdene ; lb, Ardennen ), also known as the Ardennes Forest or Forest of Ardennes, is a region of extensive forests, rough terrain, rolling hills and ridges primarily in Be ...
, Belgium
Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...
* Ibitiara, Bahia
Bahia ( , , ; meaning "bay") is one of the 26 states of Brazil, located in the Northeast Region of the country. It is the fourth-largest Brazilian state by population (after São Paulo, Minas Gerais, and Rio de Janeiro) and the 5th-largest b ...
, Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
* Nagano Prefecture, Japan
* Near Ogilby, Imperial County at Tres Cerritos, Mariposa County
Mariposa County () is a county in the U.S. state of California. As of the 2020 U.S. Census, the population was 17,131. The county seat is Mariposa. It is located in the western foothills of the Sierra Nevada mountains, north of Fresno, east of ...
, and the Champion mine, White Mountains, Mono County, California
Mono County ( ) is a county located in the east central portion of the U.S. state of California. As of the 2020 census, the population was 13,195, making it the fourth-least populous county in California. The county seat is Bridgeport. The coun ...
, USA
* Near Quartzsite
Quartzsite is a town in La Paz County, Arizona, United States. According to the 2020 census, the population was 2,413.
Interstate 10 runs directly through Quartzsite which is at the intersection of U.S. Route 95 and Arizona State Route 95 wi ...
, La Paz County, Arizona, USA
* Large deposits at the Deep River region of North Carolina
North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and ...
, USA
*Graves Mountain, Lincoln County, Georgia
Lincoln County is a county located in the east central portion of the U.S. state of Georgia. As of the 2020 census, the population was 7,690. The county seat is Lincolnton. The county was created on February 20, 1796.
Lincoln County is includ ...
, USA
In South Africa, major deposits of pyrophyllite occur within the Ottosdal
Ottosdal is a small town situated at an altitude of 1,479 meters (4,855 feet) on the branch railway line from Makwassie in the central North West Province of South Africa. Ottosdal is a farming community engaged in the growing of grains such as m ...
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.[Nel, LT., H. Jacobs, J.T. Allen and G.R. Bozzoli 1937. ''Wonderstone''. Geological Survey of South Africa Bulletin no. 8.]
Uses
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
Soapstone (also known as steatite or soaprock) is a talc-schist, which is a type of metamorphic rock. It is composed largely of the magnesium rich mineral talc. It is produced by dynamothermal metamorphism and metasomatism, which occur in the ...
and pinite) used for these Chinese carvings are included with pyrophyllite under the terms agalmatolite
Pagodite or agalmatolite is a variety of pyrophyllite used by Chinese artisans for carvings in pagodas and similar objects. Usually soft and sometimes soapy, it can be a greyish green or greyish yellow colour.[< ...]
and pagodite.
Pyrophyllite is easily machineable and has excellent thermal stability, so 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
Some seals and gaskets
A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. It is a deformable material that is used to c ...
material and as a pressure-transmitting medium.
See also
*
References
.
External links
Mineral galleries
USGS
{{1911, wstitle=Pyrophyllite, volume=22, pages=695–696
Phyllosilicates
Aluminium minerals
Triclinic minerals
Monoclinic minerals
Minerals in space group 2
Minerals in space group 15
Luminescent minerals