Talc

Talc is a clay mineral composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often in combination with corn starch, is widely used as baby powder. This mineral is used as a thickening agent and lubricant, is an ingredient in ceramics, paint and roofing material, and is also one of the main ingredients in many cosmetic products.[5] It occurs as foliated to fibrous masses, and in an exceptionally rare crystal form. It has a perfect basal cleavage, uneven flat fracture and it is foliated with a two dimensional platy form.

The Mohs scale of mineral hardness is based on scratch hardness comparison, ranging from 1-10, a value of 10 being the hardest of minerals. Talc is the defining value 1 therefore the softest of minerals. Any mineral below a value of 2 on Mohs scale of mineral hardness can be scratched by a fingernail. When scraped on a streak plate it produces a white streak, though this indicator is of little importance because most silicate minerals produce a white streak. Talc is translucent to opaque with colors ranging from whitish grey to green with a vitreous and pearly luster. Talc is not soluble in water, but is slightly soluble in dilute mineral acids.[6]

Soapstone is a well known metamorphic rock composed predominantly of talc.

Talc
Talc-usa10b
General
CategorySilicate mineral
Formula
(repeating unit)
Mg3Si4O10(OH)2
Strunz classification9.EC.05
Crystal systemMonoclinic or triclinic[1]
Crystal classEither prismatic (2m) or pinacoidal (1)[2]
Unit cella = 5.291 Å, b = 9.173 Å
c = 5.290 Å; α = 98.68°
β = 119.90°, γ = 90.09°; Z = 2 or
a = 5.287 Å, b = 9.158 Å
c = 18.95 [Å], β = 99.3°; Z = 4[2]
Identification
ColorLight to dark green, brown, white, grey
Crystal habitFoliated to fibrous masses, rare as platey to pyramidal crystals
CleavagePerfect on {001} basal cleavage
FractureFlat surfaces (not cleavage), fracture in an uneven pattern
TenacitySectile
Mohs scale hardness1 (defining mineral)
LusterWaxlike or pearly
StreakWhite jot to pearl black
DiaphaneityTranslucent
Specific gravity2.58 to 2.83
Optical propertiesBiaxial (-)
Refractive indexnα = 1.538 – 1.550
nβ = 1.589 – 1.594
nγ = 1.589 – 1.600
Birefringenceδ = 0.051
PleochroismWeak in dark varieties
Ultraviolet fluorescenceShort UV=orange yellow, long UV=yellow
References[2][3][4]

Etymology

The word "talc" derives from Medieval Latin talcum, which in turn originates from Arabic: طلقṭalq which, derives from Persian: تالکtālk. In ancient times, the word was used for various related minerals, including talc, mica, and selenite.[7]

Formation

Talc block
A block of talc

Talc is a mineral that results from the metamorphism of magnesian minerals such as serpentine, pyroxene, amphibole, and olivine, in the presence of carbon dioxide and water. This is known as "talc carbonation" or "steatization" and produces a suite of rocks known as talc carbonates.

Talc is primarily formed by hydration and carbonation by this reaction:

+ + +

Talc can also be formed via a reaction between dolomite and silica, which is typical of skarnification of dolomites by silica-flooding in contact metamorphic aureoles:

+ + + +

Talc can also be formed from magnesian chlorite and quartz in blueschist and eclogite metamorphism by the following metamorphic reaction:

chlorite + quartzkyanite + talc + water

In this reaction, the ratio of talc and kyanite depends on aluminium content, with more aluminous rocks favoring production of kyanite. This is typically associated with high-pressure, low-temperature minerals such as phengite, garnet, and glaucophane within the lower blueschist facies. Such rocks are typically white, friable, and fibrous, and are known as whiteschist.

Talc is a trioctahedral layered mineral; its structure is similar to pyrophyllite, but with magnesium in the octahedral sites of the composite layers.[1]

Occurrence

2005talc
Talc output in 2005

Talc is a common metamorphic mineral in metamorphic belts that contain ultramafic rocks, such as soapstone (a high-talc rock), and within whiteschist and blueschist metamorphic terranes. Prime examples of whiteschists include the Franciscan Metamorphic Belt of the western United States, the western European Alps especially in Italy, certain areas of the Musgrave Block, and some collisional orogens such as the Himalayas, which stretch along Pakistan, India, Nepal, and Bhutan.

Talc carbonate ultramafics are typical of many areas of the Archaean cratons, notably the komatiite belts of the Yilgarn Craton in Western Australia. Talc-carbonate ultramafics are also known from the Lachlan Fold Belt, eastern Australia, from Brazil, the Guiana Shield, and from the ophiolite belts of Turkey, Oman, and the Middle East.

China is the key world talc and steatite producing country with an output of about 2.2M tonnes(2016), which accounts for 30% of total global output. The other major producers are Brazil (12%), India (11%), the U.S. (9%), France (6%), Finland (4%), Italy, Russia, Canada, and Austria (2%, each).[8]

Notable economic talc occurrences include the Mount Seabrook talc mine, Western Australia, formed upon a polydeformed, layered ultramafic intrusion. The France-based Luzenac Group is the world's largest supplier of mined talc. Its largest talc mine at Trimouns near Luzenac in southern France produces 400,000 tonnes of talc per year.

Conflict mineral

Extraction in disputed areas of Nangarhar province, Afghanistan, has led the international monitoring group Global Witness to declare talc a conflict mineral, as the profits are used to fund armed confrontation between the Taliban and Islamic State.[9]

Uses

Talcum Powder.JPEG
Talcum powder
Talc
The structure of talc is composed of Si2O5 sheets with magnesium sandwiched between sheets in octahedral sites.

Talc is used in many industries, including paper making, plastic, paint and coatings, rubber, food, electric cable, pharmaceuticals, cosmetics, and ceramics. A coarse grayish-green high-talc rock is soapstone or steatite, used for stoves, sinks, electrical switchboards, etc. It is often used for surfaces of laboratory table tops and electrical switchboards because of its resistance to heat, electricity and acids. In finely ground form, talc finds use as a cosmetic (talcum powder), as a lubricant, and as a filler in paper manufacture. It is used to coat the insides of inner tubes and rubber gloves during manufacture to keep the surfaces from sticking. Talcum powder, with heavy refinement, has been used in baby powder, an astringent powder used to prevent diaper rash. The American Academy of Pediatrics recommends that parents not use baby powder because it poses a risk of respiratory problems, including breathing trouble and serious lung damage if the baby inhales it. The small size of the particles makes it difficult to keep them out of the air while applying the powder. Zinc oxide-based ointments are a much safer alternative.[10]

It is also often used in basketball to keep a player's hands dry. Most tailor's chalk, or French chalk, is talc, as is the chalk often used for welding or metalworking.

Talc is also used as food additive or in pharmaceutical products as a glidant. In medicine, talc is used as a pleurodesis agent to prevent recurrent pleural effusion or pneumothorax. In the European Union, the additive number is E553b.
Talc may be used in the processing of white rice as a buffing agent in the polishing stage.

Due to its low shear strength, talc is one of the oldest known solid lubricants. Also a limited use of talc as friction-reducing additive in lubricating oils is made.[11]

Talc is widely used in the ceramics industry in both bodies and glazes. In low-fire art-ware bodies, it imparts whiteness and increases thermal expansion to resist crazing. In stonewares, small percentages of talc are used to flux the body and therefore improve strength and vitrification. It is a source of MgO flux in high-temperature glazes (to control melting temperature). It is also employed as a matting agent in earthenware glazes and can be used to produce magnesia mattes at high temperatures.

ISO standard for quality (ISO 3262)

Type Talc content min. wt% Loss on ignition at 1000 °C, wt % Solubility in HCl, max. wt %
A 95 4 – 6.5 5
B 90 4–9 10
C 70 4–18 30
D 50 4–27 30

Patents are pending on the use of magnesium silicate as a cement substitute. Its production requirements are less energy-intensive than ordinary Portland cement (at a heating requirement of around 650 °C for talc compared to 1500 °C for limestone to produce Portland cement), while it absorbs far more carbon dioxide as it hardens. This results in a negative carbon footprint overall, as the cement substitute removes 0.6 tonnes of CO2 per tonne used. This contrasts with a positive carbon footprint of 0.4 tonne per tonne of conventional cement.[12]

Talc is used in the production of the materials that are widely used in the building interiors such as base content paints in wall coatings. Other areas that use talc to a great extent are organic agriculture, food industry, cosmetics, and hygiene products such as baby powder and detergent powder.

Talc is sometimes used as an adulterant to illegal heroin, to expand volume and weight and thereby increase its street value. With intravenous use, it may lead to pulmonary talcosis, a granulomatous inflammation in the lungs.

Sterile talc powder

Sterile talc powder (NDC 63256-200-05) is a sclerosing agent used in the procedure of pleurodesis. This can be helpful as a cancer treatment to prevent pleural effusions (an abnormal collection of fluid in the space between the lungs and the thoracic wall). It is inserted into the space via a chest tube, causing it to close up, so fluid cannot collect there. The finished product has been sterilized by gamma irradiation.

Safety

Talc powder is a household item, sold globally for use in personal hygiene and cosmetics. Suspicions have been raised that its use contributes to certain types of disease, mainly cancers of the ovaries and lungs. It is classified as a group 3 agent in the IARC listing.[13] Reviews by Cancer Research UK and the American Cancer Society conclude that some studies have found a link, but other studies have not.[14][15]

The studies discuss pulmonary issues,[16] lung cancer,[17][18] and ovarian cancer.[19] One of these, published in 1993, was a US National Toxicology Program report, which found that cosmetic grade talc containing no asbestos-like fibres was correlated with tumor formation in rats forced to inhale talc for 6 hours a day, five days a week over at least 113 weeks.[17] A 1971 paper found particles of talc embedded in 75% of the ovarian tumors studied.[20] Research published in 1995 and 2000 concluded that it was plausible that talc could cause ovarian cancer, but no conclusive evidence was shown.[21][22]

Industrial grade

In the United States, the Occupational Safety and Health Administration and National Institute for Occupational Safety and Health have set occupational exposure limits to respirable talc dusts at 2 mg/m3 over an eight-hour workday. At levels of 1000 mg/m3, inhalation of talc is considered immediately dangerous to life and health.[23]

Food grade

The United States Food and Drug Administration considers talc (magnesium silicate) generally recognized as safe (GRAS) to use as an anticaking agent in table salt in concentrations smaller than 2%.[24]

Association with asbestos

One particular issue with commercial use of talc is its frequent co-location in underground deposits with asbestos ore. Asbestos is a general term for different types of fibrous silicate minerals, desirable in construction for their heat resistant properties.[25] There are six varieties of asbestos; the most common variety in manufacturing, white asbestos, is in the serpentine family.[26] Serpentine minerals are sheet silicates; although not in the serpentine family, talc is also a sheet silicate, with two sheets connected by magnesium cations. The frequent co-location of talc deposits with asbestos may result in contamination of mined talc with white asbestos, which poses serious health risks when dispersed into the air and inhaled. Stringent quality control since 1976, including separating cosmetic- and food-grade talc from "industrial"-grade talc, has largely eliminated this issue, but it remains a potential hazard requiring mitigation in the mining and processing of talc.[27] A 2010 US FDA survey failed to find asbestos in a variety of talc-containing products.[28] A 2018 Reuters investigation has asserted that pharmaceuticals company Johnson & Johnson knew for decades that there was asbestos in its baby powder.[29]

Litigation

In 2006 the International Agency for Research on Cancer classified talcum powder as a possible human carcinogen if used in the female genital area. Yet no federal agency in the US acted to remove talcum powder from the market or add warnings.[30]

In February 2016, as the result of a lawsuit against Johnson & Johnson (J&J), a St. Louis jury awarded $72 million to the family of an Alabama woman who died from ovarian cancer. The family claimed that the use of talcum powder was responsible for her cancer.

In May 2016, a South Dakota woman was awarded $55 million as the result of another lawsuit against J&J.[31] The woman had used Johnson & Johnson's Baby Powder for more than 35 years before being diagnosed with ovarian cancer in 2011.

In October 2016, a St. Louis jury awarded $70.1 million to a Californian woman with ovarian cancer who had used Johnson's Baby Powder for 45 years.[32]

In August 2017, a Los Angeles jury awarded $417 million to a Californian woman, Eva Echeverria, who developed ovarian cancer as a "proximate result of the unreasonably dangerous and defective nature of talcum powder", her lawsuit against Johnson & Johnson stated.[33]

At least 1,200 to 2,000 other talcum powder-related lawsuits are pending.[32][34]

On 20 October 2017, Los Angeles Superior Court judge Maren Nelson dismissed the verdict of Eva Echeverria against Johnson & Johnson and its talc-containing consumer products for causing cancer. The judge stated that Eva Echeverria proved there is "an ongoing debate in the scientific and medical community about whether talc more probably than not causes ovarian cancer and thus (gives) rise to a duty to warn", but not enough to sustain the jury's imposition of liability against Johnson & Johnson stated, and concluded that Echeverria did not adequately establish that talc causes ovarian cancer.[35][36]

In July 2018, a court in St. Louis awarded a $4.7bn claim ($4.14bn in punitive damages and $550m in compensatory damages) against J&J to 22 claimant women, concluding that the company had suppressed evidence of asbestos in its products for more than four decades.[37]

See also

References

  1. ^ a b An Introduction to the Rock-Forming Minerals, 2 ed., by W.A. Deer, R.A. Howie, and J. Zussman, 1992, Prentice Hall, ISBN 0-582-30094-0.
  2. ^ a b c Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (1995). "Talc" (PDF). Handbook of Mineralogy. II (Silica, Silicates). Chantilly, VA, US: Mineralogical Society of America. ISBN 0962209716.
  3. ^ Talc. Mindat.org
  4. ^ Talc. Webmineral
  5. ^ "Talc". Minerals Education Coalition.
  6. ^ Profiles of Drug Substances, Excipients and Related Methodology, Volume 36 ISBN 978-0-123-87667-6 p. 283
  7. ^ Harper, Douglas. "talc". Online Etymology Dictionary.
  8. ^ Sergeeva, Anna (18 July 2018). "China, Brazil, the U.S. and India Remain the Major Consumers on the Global Talc Market". IndexBox.
  9. ^ "Talc: the everyday mineral funding Afghan insurgents". Global Witness. Retrieved 24 May 2018.
  10. ^ "Is it safe to use baby powder on my baby?". Babycenter.com (2017-05-01). Retrieved on 2017-05-06.
  11. ^ Rudenko, Pavlo; Bandyopadhyay, Amit (2013). "Talc as friction reducing additive to lubricating oil". Applied Surface Science. 276: 383–389. doi:10.1016/j.apsusc.2013.03.102.
  12. ^ Jha, Alok (31 December 2008) Revealed: The cement that eats carbon dioxide, The Guardian
  13. ^ List of Classifications, International Agency for Research on Cancer
  14. ^ Talcum powder and cancer, Cancerresearch.uk
  15. ^ Talcum Powder and Cancer, American Cancer Society
  16. ^ Hollinger, MA (1990). "Pulmonary toxicity of inhaled and intravenous talc". Toxicology Letters. 52 (2): 121–7, discussion 117–9. doi:10.1016/0378-4274(90)90145-C. PMID 2198684.
  17. ^ a b National Toxicology, Program (1993). "NTP Toxicology and Carcinogenesis Studies of Talc (Non-Asbestiform) in Rats and Mice (Inhalation Studies)". National Toxicology Program Technical Report Series. 421: 1–287. PMID 12616290.
  18. ^ NIOSH Worker Notification Program. "Health effects of mining and milling talc".
  19. ^ Harlow, Cramer, Bell; et al. (1992). "Perineal exposure to talc and ovarian cancer risk". Obstetrics and Gynecology. 80 (1): 19–26. PMID 1603491.CS1 maint: Multiple names: authors list (link)
  20. ^ Henderson WJ, Joslin CA, Turnbull AC, Griffiths K (1971). "Talc and carcinoma of the ovary and cervix". J Obstet Gynaecol Br Commonw. 78 (3): 266–272. doi:10.1111/j.1471-0528.1971.tb00267.x. PMID 5558843.
  21. ^ Harlow, BL; Hartge, PA (April 1995). "A review of perineal talc exposure and risk of ovarian cancer". Regulatory Toxicology and Pharmacology. 21 (2): 254–60. doi:10.1006/rtph.1995.1039. PMID 7644715.
  22. ^ Gertig, D. M.; Hunter, D. J.; Cramer, D. W.; Colditz, G. A.; Speizer, F. E.; Willett, W. C.; Hankinson, S. E. (2 February 2000). "Prospective Study of Talc Use and Ovarian Cancer" (PDF). JNCI Journal of the National Cancer Institute. 92 (3): 249–252. doi:10.1093/jnci/92.3.249.
  23. ^ "NIOSH Pocket Guide to Chemical Hazards". Centers for Disease Control and Prevention. 2011.
  24. ^ "Code of Federal Regulations". U.S. Food and Drug Administration. 2009.
  25. ^ "Asbestos". Minerals Education Coalition.
  26. ^ Plummer, Charles C.; Carlson, Diane H.; Hammersley, Lisa (22 January 2018). Physical Geology (Sixteenth ed.). ISBN 9781260091656.
  27. ^ "Is talcum powder asbestos?". The Straight Dope. 16 February 1990. Retrieved 9 March 2019.
  28. ^ "Talc Ingredients". U.S. Food and Drug Administration. 2010.
  29. ^ "J&J knew for decades that asbestos lurked in its Baby Powder". Reuters. Retrieved 15 December 2018.
  30. ^ "$417 Million Awarded in Suit Tying Johnson's Baby Powder to Cancer". Nytimes.com. Retrieved 13 July 2018.
  31. ^ McLean, Rob (3 May 2016). "Johnson & Johnson just lost another talcum powder cancer lawsuit". CNNMoney. Retrieved 18 August 2016.
  32. ^ a b Does baby powder cause cancer? Another jury thinks so, awarding $70 million to a California woman. LA Times (2016-10-28). Retrieved on 2017-05-06.
  33. ^ Jury awards $417M in lawsuit linking talcum powder to cancer. The Chronicle Herald (21 August 2017)
  34. ^ Woman wins $55M verdict against Johnson & Johnson in cancer suit. NY Daily News (3 May 2016)
  35. ^ Bellon, Tina. "California judge tosses $417 million talc cancer verdict against..." Reuters.com. Retrieved 13 July 2018.
  36. ^ Frankel, Alison. "Dismissal of $417 million verdict v. J&J is disaster for talc..." REuters.com. Retrieved 13 July 2018.
  37. ^ Butler, Sarah (13 July 2018). "Johnson & Johnson ordered to pay $4.7bn in talc powder claim". The Guardian. Retrieved 13 July 2018.
Asbestos

Asbestos is a term used to refer to six naturally occurring silicate minerals. All are composed of long and thin fibrous crystals, each fiber being composed of many microscopic 'fibrils' that can be released into the atmosphere by abrasion and other processes. Asbestos is a well known health hazard, and use of it as a building material is now banned in many countries. Inhalation of the fibres can lead to various lung conditions, including cancer.Archaeological studies have found evidence of asbestos being used as far back as the Stone Age to strengthen ceramic pots, but large-scale mining began at the end of the 19th century when manufacturers and builders began using asbestos for its desirable physical properties. Asbestos use was widespread during the 20th century until public recognition of the health hazards, beginning in the 1970s, of asbestos dust led to its outlawing by courts and legislatures in mainstream construction and fireproofing in most countries. Despite this, at least 100,000 people a year are thought to die from diseases related to asbestos exposure.Despite the severity of asbestos-related diseases, the material has been used widely all around the world, and most pre-1980s buildings are thought to contain asbestos. Many developing countries also still support the use of asbestos as a building material, and mining of asbestos is ongoing, with the top producer Russia producing around one million metric tonnes in 2015.

Baby powder

Baby powder is an astringent powder used for preventing diaper rash, as a deodorant, and for other cosmetic uses. It may be composed of talcum (in which case it is also called talcum powder) or corn starch (in which case it is also called corn starch). Talcum powder is dangerous if inhaled since it may cause aspiration pneumonia or granuloma. Pediatricians generally prefer cornstarch to talc because it is unlikely to be easily inhaled. Baby powder can also be used as a shampoo, cleaning agent, and freshener.Some studies have found a statistical relationship between talc applied to the perineal area by women and incidence of ovarian cancer. However, there is not a consensus that the two are linked. In 2017, over 1,000 U.S. women sued Johnson & Johnson for covering up the possible cancer risk with its Baby Powder product.Baby powder is also efficient for removing greasy hair, or oil on clothes.

Cellana talcosa

Cellana talcosa, the talc limpet or turtle limpet is a species of true limpet, a marine gastropod mollusc in the family Nacellidae, which is one of the true limpet families.

This species is endemic to the Hawaiian islands, where its common name is koele or opihi ko'ele. [1] It is the largest limpet found in the Hawaiian islands and can reach 4 inches in diameter.

Coated paper

Coated paper is paper which has been coated by a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness or reduced ink absorbency. Various materials, including Kaolinite, calcium carbonate, Bentonite, and talc can be used to coat paper for high quality printing used in packaging industry and in magazines. The chalk or china clay is bound to the paper with synthetic viscosifiers, such as styrene-butadiene latexes and natural organic binders such as starch. The coating formulation may also contain chemical additives as dispersants, resins, or polyethylene to give water resistance and wet strength to the paper, or to protect against ultraviolet radiation.

Eridania Lake

Eridania Lake is a theorized ancient lake on Mars with a surface area of roughly 1.1 million square kilometers. It is located at the source of the Ma'adim Vallis outflow channel and extends into Eridania quadrangle and the Phaethontis quadrangle. As Eridania Lake dried out in the late Noachian epoch it divided into a series of smaller lakes.

Later research with CRISM found thick deposits, greater than 400 meters thick, that contained the minerals saponite, talc-saponite, Fe-rich mica (for example, glauconite-nontronite), Fe- and Mg-serpentine, Mg-Fe-Ca-carbonate and probable Fe-sulphide. The Fe-sulphide probably formed in deep water from water heated by volcanoes. Such a process, classified as hydrothermal may have been a place where life began.

Filler (materials)

Filler materials are particles added to resin or binders (plastics, composites, concrete) that can improve specific properties, make the product cheaper or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers (with a total sum of approximately $18 billion USD) are used every year in different application areas, such as paper, plastics, rubber, paints, coatings, adhesives and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black. Filler materials can affect the tensile strength, toughness, heat resistance, color, clarity etc. A good example of this is the addition of talc to polypropylene. Most of the filler materials used in plastics are mineral or glass based filler materials. There are two main subgroups of filler materials: particulates and fibers. Particulates are small particles of filler which are mixed in the matrix where size and aspect ratio are important. Fibers are small circular strands that can be very long and have very high aspect ratios.

Greenschist

Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically 300–450 °C (570–840 °F) and 2–10 kilobars (14,500–58,000 psi). Greenschists commonly have an abundance of green minerals such as chlorite, serpentine, and epidote, and platy minerals such as muscovite and platy serpentine. The platiness causes the tendency to split, or have schistosity. Other common minerals include quartz, orthoclase, talc, carbonate minerals and amphibole (actinolite).Greenschist is a general field petrologic term for metamorphic or altered mafic volcanic rock. In Europe, the term prasinite is sometimes used. A greenstone is sometimes a greenschist but can also be rock types without any schistosity, especially metabasalt (spilite or picrite). The green is due to abundant green chlorite, actinolite and epidote minerals that dominate the rock. However, basalts may remain quite black if primary pyroxene does not revert to chlorite or actinolite. To qualify for the name a rock must also exhibit schistosity or some foliation or layering. The rock is derived from basalt, gabbro or similar rocks containing sodium-rich plagioclase feldspar, chlorite, epidote and quartz.

Imerys

Imerys S.A. is a French multinational company which specialises in the production and processing of industrial minerals. It is headquartered in Paris and is a constituent of the CAC Mid 60 index.

Imerys has operations in 50 countries and has more than 18,000 employees. It extracts and processes rocks and minerals on behalf of customers in the manufacturing and construction industries.

Groupe Bruxelles Lambert is the largest shareholder of Imerys.

Komatiite

Komatiite ( ) is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava with ≥ 18 wt% MgO. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content. Komatiite was named for its type locality along the Komati River in South Africa, and frequently displays spinifex texture composed of large dendritic plates of olivine and pyroxene.

Komatiites are rare and predominantly found in rocks of Archaean age, with few Proterozoic or Phanerozoic komatiites known. This restriction in age is thought to be due to cooling of the mantle, which may have been 100 – 250°C hotter during the Archaean (4.0 to 2.5 billion years ago). The early Earth had much higher heat production, due to the residual heat from planetary accretion, as well as the greater abundance of radioactive elements. Lower temperature mantle melts such as basalt and picrite have essentially replaced komatiites as an eruptive lava on the Earth's surface.

Geographically, komatiites are predominantly restricted in distribution to the Archaean shield areas, and occur with other ultramafic and high-magnesian mafic volcanic rocks in Archaean greenstone belts. The youngest komatiites are from the island of Gorgona on the Caribbean oceanic plateau off the Pacific coast of Colombia, and a rare example of Proterozoic komatiite is found in the Winnipegosis komatiite belt, Manitoba, Canada.

Mining in Austria

Mining in Austria is an industry on the decline.

After a period of postwar expansion, mineral production has stagnated in recent decades, and metals mining continues to decline, because of high operating costs, increased foreign competition, low ore grades, and environmental problems. All the metal mines in the country were closed, except an iron ore operation at the Erzberg mine (producing 1.8 million tons of iron ore and concentrate in 2000) and a tungsten operation at the Mittersill mine, which was the West's largest underground tungsten mine. Most of the growth in the mineral resources area was in the production of industrial minerals, the area in which future mining activities will most likely be concentrated, mostly for domestic consumption.

Noonday Camp, California

Noonday Camp, also known as Mill City, Noonday City, and Tecopa, is a ghost town located in the Mojave Desert east of Tecopa in Inyo County, California.

Upper Noonday Camp is located at 35°48′39″N 116°06′15″W, while Lower Noonday Camp is located just south of it at 35°48′01″N 116°06′05″W.

Pleurodesis

Pleurodesis is a medical procedure in which the pleural space is artificially obliterated. It involves the adhesion of the two pleurae.

Prehnite-pumpellyite facies

The prehnite-pumpellyite facies is a metamorphic facies typical of subseafloor alteration of the oceanic crust around mid-ocean ridge spreading centres.

It is a metamorphic grade transitional between zeolite facies and greenschist facies representing a temperature range of 250 to 350 °C and a pressure range of approximately two to seven kilobars. The mineral assemblage is dependent on host composition.

In mafic rocks the assemblage is chlorite, prehnite, albite, pumpellyite and epidote.

In ultramafic rocks the assemblage is serpentine, talc, forsterite, tremolite and chlorite.

In argillaceous sedimentary rocks the assemblage is quartz, illite, albite, and stilpnomelane chlorite.

In carbonate sediments the assemblage is calcite, dolomite, quartz, clays, talc, and muscovite.

Pulmonary talcosis

Pulmonary talcosis is a pulmonary disorder caused by talc.

It has been related to silicosis resulting from inhalation of talc and silicates. It is also tied to heroin use where talc might be used as an adulterant to increase weight and street value. It is one of several noted associations and possible risks of street heroin use. Talcosis can also arise from the injection of drugs intended for oral administration, as talc is present in many tablets and capsules that are used intravenously, such as benzodiazepines, dextroamphetamine, and prescription opioids.

Reynès

Reynès (Catalan: Reiners) is a commune in the Pyrénées-Orientales department in southern France.

Schist

Schist (pronounced SHIST) is a medium-grade metamorphic rock. Schist has medium to large, flat, sheet-like grains in a preferred orientation (nearby grains are roughly parallel). It is defined by having more than 50% platy and elongated minerals (such as micas or talc), often finely interleaved with quartz and feldspar. These lamellar (flat, planar) minerals include 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 produced. Schist is often garnetiferous. Schist forms at a higher temperature and has larger grains than phyllite. Geological foliation (metamorphic arrangement in layers) with medium to large grained flakes in a preferred sheetlike orientation is called schistosity.The names of various schists are derived from their mineral constituents. For example, schists primarily composed of biotite and muscovite are called mica schists. Most schists are mica schists, but graphite and chlorite schists are also common. Schists are also named for their prominent or perhaps unusual mineral constituents, as in the case of garnet schist, tourmaline schist, and glaucophane schist.

The individual mineral grains in schist, drawn out into flaky scales by heat and pressure, can be seen with the naked eye. Schist is characteristically foliated, meaning that the individual mineral grains split off easily into flakes or slabs. The word schist is derived ultimately from the Greek word σχίζειν (schízein) meaning "to split", which is a reference to the ease with which schists can be split along the plane in which the platy minerals lie.

Most schists are derived from clays and muds that have passed through a series of metamorphic processes involving the production of shales, slates and phyllites as intermediate steps. Certain schists are derived from fine-grained igneous rocks such as basalts and tuffs.

Soapstone

Soapstone (also known as steatite or soaprock) is a talc-schist, which is a type of metamorphic rock. It is largely composed of the mineral talc, and thus is rich in magnesium. It is produced by dynamothermal metamorphism and metasomatism, which occur in the zones where tectonic plates are subducted, changing rocks by heat and pressure, with influx of fluids, but without melting. It has been a medium for carving for thousands of years.

Talc carbonate

Talc carbonates are a suite of rock and mineral compositions found in metamorphosed ultramafic rocks.

The term refers to the two most common end-member minerals found within ultramafic rocks which have undergone talc-carbonation or carbonation reactions: talc and the carbonate mineral magnesite.

Talc carbonate mineral assemblages are controlled by temperature and pressure of metamorphism and the partial pressure of carbon dioxide within metamorphic fluids, as well as by the composition of the host rock.

Tolland High School

Tolland High School is a public high school in Tolland, Connecticut.

Micas
Talcs
Pyrophyllite series
Kaolinites
Serpentines
Corrensites
Smectites and vermiculite family
Chlorites
Allophanes
Sepiolites
Pyrosmalites
Stilpnomelanes

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