Pyrophyllite
Encyclopedia
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 crystal
s 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
.
and schist
ose 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:
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.
), 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.
Pyrophyllite is easily machineable 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.
Silicate minerals
The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group...
mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
composed of aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
hydroxide
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
: Al2Si4O10(OH)2. It occurs in two more or less distinct varieties, namely, as crystalline folia and as compact masses; distinct crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
s 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
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
is 2.65 - 2.85. The two varieties are thus very similar to talc
Talc
Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg34 or Mg3Si4O102. In loose form, it is the widely-used substance known as talcum powder. It occurs as foliated to fibrous masses, its crystals being so rare as to be almost unknown...
.
Occurrence
Pyrophyllite occurs in phyllitePhyllite
Phyllite is a type of foliated metamorphic rock primarily composed of quartz, sericite mica, and chlorite; the rock represents a gradation in the degree of metamorphism between slate and mica schist. Minute crystals of graphite, sericite, or chlorite impart a silky, sometimes golden sheen to the...
and schist
Schist
The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...
ose rocks, often associated with kyanite
Kyanite
Kyanite, whose name derives from the Greek word kuanos sometimes referred to as "kyanos", meaning deep blue, is a typically blue silicate mineral, commonly found in aluminium-rich metamorphic pegmatites and/or sedimentary rock. Kyanite in metamorphic rocks generally indicates pressures higher than...
, of which it is an alteration product. It also occurs as hydrothermal deposits. Typical associated minerals include: kyanite, andalusite
Andalusite
Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5.The variety chiastolite commonly contains dark inclusions of carbon or clay which form a checker-board pattern when shown in cross-section....
, topaz
Topaz
Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO42. Topaz crystallizes in the orthorhombic system and its crystals are mostly prismatic terminated by pyramidal and other faces.-Color and varieties:...
, mica
Mica
The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...
and quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
.
Deposits containing well-crystallized material are found in:
- Russia - pale green foliated masses, very like talc in appearance, are found at Beresovsk near YekaterinburgYekaterinburgYekaterinburg is a major city in the central part of Russia, the administrative center of Sverdlovsk Oblast. Situated on the eastern side of the Ural mountain range, it is the main industrial and cultural center of the Urals Federal District with a population of 1,350,136 , making it Russia's...
in the UralUral MountainsThe Ural Mountains , or simply the Urals, are a mountain range that runs approximately from north to south through western Russia, from the coast of the Arctic Ocean to the Ural River and northwestern Kazakhstan. Their eastern side is usually considered the natural boundary between Europe and Asia...
s. - St. Niklas, ZermattZermattZermatt is a municipality in the district of Visp in the German-speaking section of the canton of Valais in Switzerland. It has a population of about 5,800 inhabitants....
, ValaisValaisThe Valais is one of the 26 cantons of Switzerland in the southwestern part of the country, around the valley of the Rhône from its headwaters to Lake Geneva, separating the Pennine Alps from the Bernese Alps. The canton is one of the drier parts of Switzerland in its central Rhône valley...
, SwitzerlandSwitzerlandSwitzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition.... - at Vaastana, KristianstadKristianstadKristianstad is a city and the seat of Kristianstad Municipality, Skåne County, Sweden with 35,711 inhabitants in 2010.-History:The city was founded in 1614 by King Christian IV of Denmark, the city's name literally means 'Town of Christian', as a planned city after the burning of the town of Vä...
, SwedenSwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund.... - near Ottrje, Ardennes Mountains, BelgiumBelgiumBelgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
- IbitiaraIbitiaraIbitiara is a town and municipality in the state of Bahia in the North-East region of Brazil.-References:...
, BahiaBahiaBahia is one of the 26 states of Brazil, and is located in the northeastern part of the country on the Atlantic coast. It is the fourth most populous Brazilian state after São Paulo, Minas Gerais and Rio de Janeiro, and the fifth-largest in size...
, BrazilBrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people... - Nagano PrefectureNagano Prefectureis a prefecture of Japan located in the Chūbu region of the island of Honshū. The capital is the city of Nagano.- History :Nagano was formerly known as the province of Shinano...
, JapanJapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south... - Manuels, Newfoundland and LabradorNewfoundland and LabradorNewfoundland and Labrador is the easternmost province of Canada. Situated in the country's Atlantic region, it incorporates the island of Newfoundland and mainland Labrador with a combined area of . As of April 2011, the province's estimated population is 508,400...
, Canada - USA
- It is found near OgilbyOgilbyOgilby may refer to:*John Ogilby, a Scottish translator, impresario and cartographer*William Ogilby, an Irish barrister and naturalist*James Douglas Ogilby , an Australian zoologist, son of William Ogilby...
, Imperial CountyImperial County, CaliforniaImperial County is a county located in the Imperial Valley, in the far southeast of the U.S. state of California, bordering both Arizona and Mexico. It is part of the El Centro Metropolitan Area, which encompasses all of Imperial County. The population as of 2000 was 142,361. The county seat is the...
at Tres Cerritos, Mariposa CountyMariposa County, CaliforniaMariposa County is a county in the U.S. state of California, located in the western foothills of the Sierra Nevada mountains. It lies north of Fresno, east of Merced, and southeast of Stockton. As of the 2010 census, the population was 18,251 up from 17,130 at the 2000 census...
, and the Champion mine, White Mountains, Mono County, CaliforniaMono County, CaliforniaMono County is a county located in the east central portion of the U.S. state of California, to the east of the Sierra Nevada between Yosemite National Park and Nevada. As of the 2010 census, the population was 14,202, up from 12,853 at the 2000 census... - near Quartzsite, La Paz County, ArizonaLa Paz County, ArizonaLa Paz County is a county in the western part of the U.S. state of Arizona. As of the 2010 census its population was 20,489. The county seat is Parker...
- the large deposits at the Deep RiverDeep River (North Carolina)The Deep River is a tributary of the Cape Fear River, approximately 125 miles long, in north central North Carolina in the United States.- Course :...
region of North CarolinaNorth CarolinaNorth Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte... - Graves Mountain, Lincoln County, GeorgiaLincoln County, GeorgiaLincoln County is a county located in the U.S. state of Georgia, with the Savannah River forming its northeastern border. Located above the fall line, it is part of the Central Savannah River Area and a member of the CSRA Regional Development Center. The county was created on February 20, 1796. ...
- It is found near Ogilby
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.
Uses
The compact variety of pyrophyllite is used for slate pencils and tailors chalk (French chalkFrench chalk
French chalk is a form of steatite.As an arist's material the term is used by Max Doerner in his book "The Materials of the Artist" where he describes a calcium carbonate used to make traditional gesso primer, to be painted over...
), 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.
Pyrophyllite is easily machineable 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
Pressure experiment
Pressure experiments are experiments performed at pressures lower or higher than atmospheric pressure, called low-pressure experiments and high-pressure experiments, respectively. Pressure experiment are necessary because substances behave differently at different pressures. For example, water...
experiments, both as a gasket
Diamond anvil cell
A diamond anvil cell is a device used in scientific experiments. It allows compressing a small piece of material to extreme pressures, which can exceed 3,000,000 atmospheres ....
material and as a pressure-transmitting medium.