Asbestos

Asbestos (pronounced: /æsˈbɛstəs/ or /æsˈbɛstɒs/) 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 asbestosis and cancer.[1]

Archaeological studies have found evidence of asbestos being used as far back as the Stone Age to strengthen ceramic pots,[2] 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.[3] Despite this, at least 100,000 people a year are thought to die from diseases related to asbestos exposure.[4]

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.[5] 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.[4]

Asbestos
Asbestos with muscovite
Fibrous tremolite asbestos on muscovite
General
CategorySilicate minerals
Strunz classification09.ED.15
Dana classification71.01.02d.03
Crystal systemOrthorhombic, monoclinic
Identification
Formula mass277.11 g
ColorGreen, red, yellow, white, gray, blue
Crystal habitAmorphous, granular, massive
CleavagePrismatic
FractureFibrous
Mohs scale hardness2.5–6.0
LusterSilky
StreakWhite
Specific gravity2.4–3.3
Optical propertiesBiaxial
Refractive index1.53–1.72
Birefringence0.008
2V angle20° to 60°
DispersionRelatively weak
ExtinctionParallel or oblique
Ultraviolet fluorescenceNon-fluorescent
Melting point400 to 1,040 °C (752 to 1,904 °F)

Etymology

The word "asbestos", first used in the 1600s, ultimately derives from the Ancient Greek ἄσβεστος, meaning “unquenchable” or “inextinguishable”.[6][7][8] The name reflects use of the substance for wicks that would never burn up.[6]

It was adopted via the Old French abestos, which in turn got the word from Greek via Latin, but in the original Greek, it actually referred to quicklime. It is said by the Oxford English Dictionary to have been wrongly used by Pliny for asbestos, who popularized the misnomer. Asbestos was referred to in Greek as amiantos, meaning "undefiled", because it was not marked when thrown into a fire. This is the source for the word for asbestos in many languages, such as the Portuguese amianto. It had also been called "amiant" in English in the early 15th century, but this usage was superseded by "asbestos".[9] The word is pronounced /æsˈbɛstəs/ or /æsˈbɛstɒs/.[10]

History

People have used asbestos for thousands of years to create flexible objects, such as napkins, that resist fire. In the modern era, companies began producing asbestos consumer goods on an industrial scale. Now people recognize the health hazard that asbestos dust poses, and it is banned or strictly regulated around the world.

Early uses

Asbestos use dates back at least 4,500 years, when the inhabitants of the Lake Juojärvi region in East Finland strengthened earthenware pots and cooking utensils with the asbestos mineral anthophyllite (see Asbestos-ceramic).[11] One of the first descriptions of a material that may have been asbestos is in Theophrastus, On Stones, from around 300 BC, although this identification has been questioned.[12] In both modern and ancient Greek, the usual name for the material known in English as "asbestos" is amiantos ("undefiled", "pure"), which was adapted into the French as amiante and into Spanish and Portuguese as amianto. In modern Greek, the word ἀσβεστος or ασβέστης stands consistently and solely for lime.

The term asbestos is traceable to Roman naturalist Pliny the Elder's manuscript Natural History, and his use of the term asbestinon, meaning "unquenchable".[6][7][11] While Pliny or his nephew Pliny the Younger is popularly credited with recognising the detrimental effects of asbestos on human beings,[13] examination of the primary sources reveals no support for either claim.[14]

Wealthy Persians amazed guests by cleaning a cloth by exposing it to fire. For example, according to Tabari, one of the curious items belonging to Khosrow II Parviz, the great Sassanian king (r. 531–579), was a napkin (Persian: منديل‎) that he cleaned simply by throwing it into fire. Such cloth is believed to have been made of asbestos imported over the Hindu Kush.[15] According to Biruni in his book, Gems, any cloths made of asbestos (Persian: آذرشست‎, āzarshost) were called shostakeh (Persian: شستكه‎).[16] Some Persians believed the fiber was the fur of an animal, called the samandar (Persian: سمندر‎), which lived in fire and died when exposed to water,[17][18] which was where the former belief that the salamander could tolerate fire originated.[19]

Charlemagne, the first Holy Roman Emperor (800–814), is said to have had a tablecloth made of asbestos.[20]

Marco Polo recounts having been shown, in a place he calls Ghinghin talas, "a good vein from which the cloth which we call of salamander, which cannot be burnt if it is thrown into the fire, is made ..."[21]

Some archaeologists believe that ancients made shrouds of asbestos, wherein they burned the bodies of their kings, in order to preserve only their ashes, and prevent them being mixed with those of wood or other combustible materials commonly used in funeral pyres.[22][23] Others assert that the ancients used asbestos to make perpetual wicks for sepulchral or other lamps.[17] A famous example is the golden lamp asbestos lychnis, which the sculptor Callimachus made for the Erechtheion.[24] In more recent centuries, asbestos was indeed used for this purpose. Although asbestos causes skin to itch upon contact, ancient literature indicates that it was prescribed for diseases of the skin, and particularly for the itch. It is possible that they used the term asbestos for soapstone, because the two terms have often been confused throughout history.[22]

Industrial era

Asbestos mining 1876
Industrial scale asbestos mining began in 1878 in Thetford township, Quebec. By 1895, mining was increasingly mechanized.

The large-scale asbestos industry began in the mid-19th century. Early attempts at producing asbestos paper and cloth in Italy began in the 1850s, but were unsuccessful in creating a market for such products. Canadian samples of asbestos were displayed in London in 1862, and the first companies were formed in England and Scotland to exploit this resource. Asbestos was first used in the manufacture of yarn, and German industrialist Louis Wertheim adopted this process in his factories in Germany. [25] In 1871, the Patent Asbestos Manufacturing Company was established in Glasgow, and during the following decades, the Clydebank area became a centre for the nascent industry.[26]

Asbestos, Quebec, Canada
Canada's biggest power shovel loading an ore train with asbestos at the Jeffrey Mine, Johns-Manville Co., Asbestos, Quebec, June 1944.

Industrial-scale mining began in the Thetford hills, Quebec, from the 1870s. Sir William Edmond Logan was the first to notice the large deposits of chrysotile in the hills in his capacity as head of Geological Survey of Canada. Samples of the minerals from here were displayed in London, and excited much interest.[25] With the opening up of the Quebec Central Railway in 1876, mining entrepreneurs such as Andrew Stuart Johnson established the asbestos industry in the province.[27] The 50 ton output of the mines in 1878 rose to over 10,000 tons in the 1890s with the adoption of machine technologies and expanded production.[25][28] For a long time, the world's largest asbestos mine was the Jeffrey mine in the town of Asbestos, Quebec.[29]

Asbestos iron ad
The applications of asbestos multiplied at the end of the 19th century. This is an advertisement for an asbestos-lined clothes iron from 1906.

Asbestos production began in the Urals of the Russian Empire in the 1880s, and in the Alpine regions of Northern Italy with the formation in Turin of the Italo-English Pure Asbestos Company in 1876, although this was soon swamped by the greater production levels from the Canadian mines. Mining also took off in South Africa from 1893 under the aegis of the British businessman Francis Oates, the Director of the De Beers company.[30] It was in South Africa that the production of amosite began in 1910. The U.S. asbestos industry had an early start in 1858, when fibrous anthophyllite was mined for use as asbestos insulation by the Johns Company, a predecessor to the current Johns Manville, at a quarry at Ward's Hill on Staten Island, New York.[31] US production began in earnest in 1899, with the discovery of large deposits in the Belvidere Mountain.

The use of asbestos became increasingly widespread towards the end of the 19th century, when its diverse applications included fire-retardant coatings, concrete, bricks, pipes and fireplace cement, heat-, fire-, and acid-resistant gaskets, pipe insulation, ceiling insulation, fireproof drywall, flooring, roofing, lawn furniture, and drywall joint compound. In 2011, it was reported that over 50% of UK houses still contained asbestos, despite a ban on asbestos products some years earlier.[32]

In Japan, particularly after World War II, asbestos was used in the manufacture of ammonium sulfate for purposes of rice production, sprayed upon the ceilings, iron skeletons, and walls of railroad cars and buildings (during the 1960s), and used for energy efficiency reasons as well. Production of asbestos in Japan peaked in 1974 and went through ups and downs until about 1990, when production began to drop dramatically.[33]

Discovery of toxicity

In 1899, Montague Murray noted the negative health effects of asbestos.[34] The first documented death related to asbestos was in 1906.[35]

In the early 1900s, researchers began to notice a large number of early deaths and lung problems in asbestos-mining towns. The first such study was conducted by H. Montague Murray at the Charing Cross Hospital, London, in 1900, in which a postmortem investigation of a young man who had died from pulmonary fibrosis after having worked for 14 years in an asbestos textile factory, discovered asbestos traces in the victim's lungs. Adelaide Anderson, the Inspector of Factories in Britain, included asbestos in a list of harmful industrial substances in 1902. Similar investigations were conducted in France and Italy, in 1906 and 1908, respectively.[36]

Heat-resistant asbestos fabric
Asbestos fabric

The first diagnosis of asbestosis was made in the UK in 1924.[35][37][38] Nellie Kershaw was employed at Turner Brothers Asbestos in Rochdale, Greater Manchester, England from 1917, spinning raw asbestos fibre into yarn.[38][39] Her death in 1924 led to a formal inquest. Pathologist William Edmund Cooke testified that his examination of the lungs indicated old scarring indicative of a previous, healed, tuberculosis infection, and extensive fibrosis, in which were visible "particles of mineral matter ... of various shapes, but the large majority have sharp angles."[37] Having compared these particles with samples of asbestos dust provided by S. A. Henry, His Majesty's Medical Inspector of Factories, Cooke concluded that they "originated from asbestos and were, beyond a reasonable doubt, the primary cause of the fibrosis of the lungs and therefore of death".[38][40]

As a result of Cooke's paper, parliament commissioned an inquiry into the effects of asbestos dust by E. R. A. Merewether, Medical Inspector of Factories, and C. W. Price, a factory inspector and pioneer of dust monitoring and control.[41] Their subsequent report, Occurrence of Pulmonary Fibrosis & Other Pulmonary Affections in Asbestos Workers, was presented to parliament on 24 March 1930.[42] It concluded that the development of asbestosis was irrefutably linked to the prolonged inhalation of asbestos dust, and included the first health study of asbestos workers, which found that 66% of those employed for 20 years or more suffered from asbestosis.[41] The report led to the publication of the first Asbestos Industry Regulations in 1931, which came into effect on 1 March 1932.[43] These regulated ventilation and made asbestosis an excusable work-related disease.[44] The term mesothelioma was first used in medical literature in 1931; its association with asbestos was first noted sometime in the 1940s. Similar legislation followed in the U.S. about ten years later.

Approximately 100,000 people in the United States have died, or are terminally ill, from asbestos exposure related to ship building. In the Hampton Roads area, a shipbuilding center, mesothelioma occurrence is seven times the national rate.[45] Thousands of tons of asbestos were used in World War II ships to insulate piping, boilers, steam engines, and steam turbines. There were approximately 4.3 million shipyard workers in the United States during WWII; for every 1,000 workers about 14 died of mesothelioma and an unknown number died from asbestosis.[46]

The United States government and asbestos industry have been criticized for not acting quickly enough to inform the public of dangers, and to reduce public exposure. In the late 1970s, court documents proved that asbestos industry officials knew of asbestos dangers since the 1930s and had concealed them from the public.[46]

In Australia, asbestos was widely used in construction and other industries between 1946 and 1980. From the 1970s there was increasing concern about the dangers of asbestos, and its use was phased out. Mining ceased in 1983. The use of asbestos was phased out in 1989 and banned entirely in December 2003. The dangers of asbestos are now well known in Australia and there is help and support for sufferers from asbestosis or mesothelioma.[47]

Usage by industry and product type

Serpentine group

Guy's Hospital- Life in a London Hospital, England, 1941 D2325
In London Hospital, England, 1941, nurse arranges an asbestos blanket over an electrically heated frame to create a hood over this patient to help warm them quickly
Arcon mk post-war pre-fab
Example of asbestos cement siding and lining on a post-war temporary house in Yardley. Nearly 40,000 of these structures were built between 1946 and 1949 to house families.

Serpentine minerals have a sheet or layered structure. Chrysotile (commonly known as white asbestos) is the only asbestos mineral in the serpentine group. In the United States, chrysotile has been the most commonly used type of asbestos. According to the U.S. Environmental Protection Agency (EPA) Asbestos Building Inspectors Manual, chrysotile accounts for approximately 95% of asbestos found in buildings in the United States.[48] Chrysotile is often present in a wide variety of products and materials, including:

  • Chlor Alkali diaphragm membranes used to make chlorine (currently in the US)[49]
  • Drywall and joint compound (including texture coats)
  • Plaster
  • Gas mask filters pre-1960s and gas mask filters from the USSR
  • Vinyl floor tiles, sheeting, adhesives
  • Roofing tars, felts, siding, and shingles[50]
  • "Transite" panels, siding, countertops, and pipes
  • Popcorn ceilings, also known as acoustic ceilings
  • Fireproofing
Heat-resistant asbestos glove
An asbestos glove
  • Caulk
  • Industrial and marine gaskets
  • Brake pads and shoes
  • Stage curtains
  • Fire blankets
  • Interior fire doors
  • Fireproof clothing for firefighters
  • Thermal pipe insulation
  • Filters for removing fine particulates from chemicals, liquids and wine
  • Dental cast linings
  • HVAC flexible duct connectors
  • Drilling fluid additives
AsbestosHeatSpreaderForCooking
A household heat spreader for cooking on gas stoves, made of asbestos (probably 1950s; "Amiante pur" is French for "Pure Asbestos")

In the European Union and Australia, it has been banned as a potential health hazard[51] and is not used at all.

Amphibole group

Amphiboles including amosite (brown asbestos) and crocidolite (blue asbestos) were formerly used in many products until the early 1980s. Tremolite asbestos constituted a contaminant of many if not all naturally occurring chrysotile deposits. The use of all types of asbestos in the amphibole group was banned in much of the Western world by the mid-1980s, and in Japan by 1995.[52] Some products that included amphibole types of asbestos included the following:

  • Low density insulating board (often referred to as AIB or asbestos insulating board) and ceiling tiles;
  • Asbestos-cement pipe (still manufactured in some parts of the world[53]);
  • Asbestos cement sheets and pipes for construction, casing for water and electrical/telecommunication services;
  • Thermal and chemical insulation (e.g., fire rated doors, limpet spray, lagging and gaskets).

Cigarette manufacturer Lorillard (Kent's filtered cigarette) used crocidolite asbestos in its "Micronite" filter from 1952 to 1956.[54]

While mostly chrysotile asbestos fibers were once used in automobile brake pads, shoes, and clutch discs, contaminants of amphiboles were present. Since approximately the mid-1990s, brake pads, new or replacement, have been manufactured instead with linings made of ceramic, carbon, metallic and aramid fiber (Twaron or Kevlar—the same material used in bulletproof vests).

Artificial Christmas snow, known as flocking, was previously made with asbestos.[55] It was used as an effect in films including The Wizard of Oz and department store window displays and it was marketed for use in private homes under brand names that included "Pure White", "Snow Drift" and "White Magic".[56]

Construction

Developed countries

Asbestos ceiling
Older decorative ceilings, similar to this one, may contain small amounts of white asbestos.
Durabestos advertisement
1929 newspaper advertisement from Perth, Western Australia, for asbestos sheeting for residential building construction.

The use of asbestos in new construction projects has been banned for health and safety reasons in many developed countries or regions, including the European Union, Australia, Hong Kong, Japan, and New Zealand. A notable exception is the United States, where asbestos continues to be used in construction such as cement asbestos pipes. The 5th Circuit Court prevented the EPA from banning asbestos in 1991 because EPA research showed the ban would cost between US$450 and 800 million while only saving around 200 lives in a 13-year timeframe, and that the EPA did not provide adequate evidence for the safety of alternative products.[57] Until the mid-1980s, small amounts of white asbestos were used in the manufacture of Artex, a decorative stipple finish,[58] however, some of the lesser-known suppliers of Artex were still adding white asbestos until 1999.[59]

Prior to the ban, asbestos was widely used in the construction industry in thousands of materials. Some are judged to be more dangerous than others due to the amount of asbestos and the material's friable nature. Sprayed coatings, pipe insulation and Asbestos Insulating Board (AIB) are thought to be the most dangerous due to their high content of asbestos and friable nature. Many older buildings built before the late 1990s contain asbestos. In the United States, there is a minimum standard for asbestos surveys as described by ASTM standard E 2356–18. In the UK, the Health and Safety Executive have issued guidance called HSG264 describing how surveys should be completed although other methods can be used if they can demonstrate they have met the regulations by other means.[60] The EPA includes some, but not all, asbestos-contaminated facilities on the Superfund National Priorities List (NPL). Renovation and demolition of asbestos-contaminated buildings is subject to EPA NESHAP and OSHA Regulations. Asbestos is not a material covered under CERCLA's innocent purchaser defense. In the UK, the removal and disposal of asbestos and of substances containing it are covered by the Control of Asbestos Regulations 2006.[61]

U.S. asbestos consumption hit a peak of 804,000 tons in 1973; world asbestos demand peaked around 1977, with 25 countries producing nearly 4.8 million metric tons annually.[62]

In older buildings (e.g. those built prior to 1999 in the UK, before white asbestos was banned), asbestos may still be present in some areas. Being aware of asbestos locations reduces the risk of disturbing asbestos.[63]

Removal of asbestos building components can also remove the fire protection they provide, therefore fire protection substitutes are required for proper fire protection that the asbestos originally provided.[63][64]

Outside Europe and North America

Some countries, such as India, Indonesia, China, Russia and Brazil, have continued widespread use of asbestos. The most common is corrugated asbestos-cement sheets or "A/C sheets" for roofing and for side walls. Millions of homes, factories, schools or sheds and shelters continue to use asbestos. Cutting these sheets to size and drilling holes to receive 'J' bolts to help secure the sheets to roof framing is done on-site. There has been no significant change in production and use of A/C sheets in developing countries following the widespread restrictions in developed nations.

11 September 2001 attacks

As New York City's World Trade Center collapsed following the September 11 attacks, Lower Manhattan was blanketed in a mixture of building debris and combustible materials. This complex mixture gave rise to the concern that thousands of residents and workers in the area would be exposed to known hazards in the air and in the dust, such as asbestos, lead, glass fibers, and pulverized concrete.[65] More than 1,000 tons of asbestos are thought to have been released into the air following the buildings' destruction.[66] Inhalation of a mixture of asbestos and other toxicants is thought to be linked to the unusually high death rate from cancer of emergency service workers since the disaster.[66] Thousands more are now thought to be at risk of developing cancer due to this exposure with those who have died so far being only the "tip of the iceberg".[66] Some commentators have criticised authorities for using asbestos in the buildings' construction.

In May 2002, after numerous cleanup, dust collection, and air monitoring activities were conducted outdoors by EPA, other federal agencies, New York City, and the state of New York, New York City formally requested federal assistance to clean and test residences in the vicinity of the World Trade Center site for airborne asbestos.[65]

Asbestos contaminants in other products

Vermiculite

Vermiculite is a hydrated laminar magnesium-aluminum-iron silicate which resembles mica. It can be used for many industrial applications and has been used as insulation. Some deposits of vermiculite have been found to be contaminated with small amounts of asbestos.[67]

One vermiculite mine operated by W. R. Grace and Company in Libby, Montana exposed workers and community residents to danger by mining vermiculite contaminated with asbestos, typically richterite, winchite, actinolite or tremolite.[68] Vermiculite contaminated with asbestos from the Libby mine was used as insulation in residential and commercial buildings through Canada and the United States. W. R. Grace and Company's loose-fill vermiculite was marketed as Zonolite but was also used in sprayed-on products such as Monokote.

In 1999, the EPA began cleanup efforts in Libby and now the area is a Superfund cleanup area.[69] The EPA has determined that harmful asbestos is released from the mine as well as through other activities that disturb soil in the area.[70]

Talc

A laboratory heat spreader made of asbestos, over Teclu burner
A laboratory heat spreader made of asbestos, on tripod over a Teclu burner.

Talc can sometimes be contaminated with asbestos due to the proximity of asbestos ore (usually tremolite) in underground talc deposits.[71] By 1973, US federal law required all talc products to be asbestos-free,[72] and today there is strict quality control in the production of talc products, separating cosmetic-grade talc (e.g. talcum powder) from industrial-grade talc (often used in friction products) has largely eliminated this issue for consumers.[73]

In 2000, tests in a certified asbestos-testing laboratory found the tremolite form of amphibole asbestos used to be found in three out of eight popular brands of children's crayons that were made partly from talc: Crayola, Prang, and RoseArt.[74] In Crayola crayons, the tests found asbestos levels around 0.05% in Carnation Pink and 2.86% in Orchid; in Prang crayons, the range was from 0.3% in Periwinkle to 0.54% in Yellow; in Rose Art crayons, it was from 0.03% in Brown to 1.20% in Orange. Overall, 32 different types of crayons from these brands used to contain more than trace amounts of asbestos, and eight others contained trace amounts. The Art and Creative Materials Institute, a trade association which tested the safety of crayons on behalf of the makers, initially insisted the test results must have been incorrect, although they later said they do not test for asbestos.[74] In May 2000, Crayola said tests by Richard Lee, a materials analyst whose testimony on behalf of the asbestos industry has been accepted in lawsuits over 250 times, found its crayons tested negative for asbestos.[75] In spite of that, in June 2000 Binney & Smith, the maker of Crayola, and the other makers agreed to stop using talc in their products, and changed their product formulations in the United States.[75]

The mining company, R T Vanderbilt Co of Gouverneur, New York, which supplied the talc to the crayon makers, states that "to the best of our knowledge and belief" there is no asbestos in its talc.[76] However media reports claim that the United States Mine Safety and Health Administration (MSHA) had found asbestos in four talc samples tested in 2000.[74] The Assistant Secretary for Mine Safety and Health subsequently wrote to the news reporter, stating that "In fact, the abbreviation ND (non detect) in the laboratory report – indicates no asbestos fibers actually were found in the samples."[77] Multiple studies by mineral chemists, cell biologists, and toxicologists between 1970 and 2000 found neither samples of asbestos in talc products nor symptoms of asbestos exposure among workers dealing with talc,[78] but more recent work has rejected these conclusions in favor of "same as" asbestos risk.[79][80]

On 12 July 2018, a Missouri jury ordered Johnson & Johnson to pay a record $4.69 billion to 22 women who alleged the company's talc-based products, including its baby powder, contain asbestos and caused them to develop ovarian cancer.[81]

Types and associated fibers

Six mineral types are defined by the EPA as "asbestos" including those belonging to the serpentine class and those belonging to the amphibole class. All six asbestos mineral types are known to be human carcinogens.[82][83] The visible fibers are themselves each composed of millions of microscopic "fibrils" that can be released by abrasion and other processes.[41]

White asbestos (Chrysotile)

Chrysotile asbestos

Asbestos fibres

Asbestos fibers

Asbestos3USGOV

Asbestos

Blue asbestos

Blue asbestos (crocidolite). The ruler is 1 cm.

Blue asbestos (teased)

Blue asbestos, teased to show the fibrous nature of the mineral

Serpentine

Serpentine class fibers are curly. Chrysotile is the only member of the serpentine class.

Epa 450 2-78-014 march 1978 asbestos comparison
Size of asbestos fibers compared to other particles (USEPA, March 1978)

Chrysotile

Chrysotile, CAS No. 12001-29-5 , is obtained from serpentinite rocks which are common throughout the world. Its idealized chemical formula is Mg3(Si2O5)(OH)4.[44] Chrysotile appears under the microscope as a white fiber.

Chrysotile has been used more than any other type and accounts for about 95% of the asbestos found in buildings in America.[84] Chrysotile is more flexible than amphibole types of asbestos, and can be spun and woven into fabric. The most common use was corrugated asbestos cement roofing primarily for outbuildings, warehouses and garages. It may also be found in sheets or panels used for ceilings and sometimes for walls and floors. Chrysotile has been a component in joint compound and some plasters. Numerous other items have been made containing chrysotile including brake linings, fire barriers in fuseboxes, pipe insulation, floor tiles, residential shingles, and gaskets for high temperature equipment.

Amphibole

Amphibole class fibers are needle-like. Amosite, crocidolite, tremolite, anthophyllite and actinolite are members of the amphibole class.

Amosite

Amosite, CAS No. 12172-73-5 , often referred to as brown asbestos, is a trade name for the amphiboles belonging to the cummingtonite-grunerite solid solution series, commonly from South Africa, named as a partial acronym for "Asbestos Mines of South Africa". One formula given for amosite is Fe7Si8O22(OH)2. Amosite is seen under a microscope as a grey-white vitreous fiber. It is found most frequently as a fire retardant in thermal insulation products, asbestos insulating board and ceiling tiles.[84]

Crocidolite

Crocidolite, CAS No. 12001-28-4 , commonly known as blue asbestos, is the fibrous form of the amphibole riebeckite, found primarily in southern Africa, but also in Australia and Bolivia. One formula given for crocidolite is Na2FeII
3
FeIII
2
Si8O22(OH)2. Crocidolite is seen under a microscope as a blue fiber.

Crocidolite commonly occurs as soft friable fibers. Asbestiform amphibole may also occur as soft friable fibers but some varieties such as amosite are commonly straighter. All forms of asbestos are fibrillar in that they are composed of fibers with breadths less than 1 micrometer in bundles of very great widths. Asbestos with particularly fine fibers is also referred to as "amianthus".

Other materials

Other regulated asbestos minerals, such as tremolite asbestos, CAS No. 77536-68-6 , Ca2Mg5Si8O22(OH)2; actinolite asbestos, CAS No. 77536-66-4, Ca2(Mg,FeII)5(Si8O22)(OH)2; and anthophyllite asbestos, CAS No. 77536-67-5 , (Mg,FeII)7Si8O22(OH)2; are less commonly used industrially but can still be found in a variety of construction materials and insulation materials and have been used in a few consumer products.

Other natural asbestiform minerals, such as richterite, Na(CaNa)(Mg,FeII)5(Si8O22)(OH)2, and winchite, (CaNa)Mg4(Al,FeIII)(Si8O22)(OH)2, though not regulated, are said by some to be no less harmful than tremolite, amosite, or crocidolite.[85] They are termed "asbestiform" rather than asbestos. Although the U.S. Occupational Safety and Health Administration (OSHA) has not included them in the asbestos standard, NIOSH and the American Thoracic Society have recommended them for inclusion as regulated materials because they may also be hazardous to health.[85]

Production

Asbestos-world-production-1900-2100
World production of asbestos (metric tons) from 1900 to the present, also including a trend line.

In 2017, 1.3 million tonnes of asbestos was mined worldwide. Russia was the largest producer with 53% of the world total, followed by Kazakhstan (16%), China (15%), and Brazil (11.5%).[86][87] Asia consumes some 70% of the asbestos produced in the world with China, India and Indonesia the largest consumers.[88]

In 2009, about 9% of the world's asbestos production was mined in Canada.[89] In late 2011, Canada's remaining two asbestos mines, both located in Quebec, halted operations.[90] In September 2012, the Quebec government halted asbestos mining.[91]

Health impact

Asbestos warning label
Asbestos warning label.
MesotheliomaCT
Left-sided mesothelioma (seen on the right of the picture): chest CT

All types of asbestos fibers are known to cause serious health hazards in humans and animals.[92][93][94] Amosite and crocidolite are considered the most hazardous asbestos fiber types; however, chrysotile asbestos has also produced tumors in animals and is a recognized cause of asbestosis and malignant mesothelioma in humans,[95] and mesothelioma has been observed in people who were occupationally exposed to chrysotile, family members of the occupationally exposed, and residents who lived close to asbestos factories and mines.[96]

During the 1980s and again in the 1990s, it was suggested at times that the process of making asbestos cement could "neutralize" the asbestos, either via chemical processes or by causing cement to attach to the fibers and changing their physical size; subsequent studies showed that this was untrue, and that decades-old asbestos cement, when broken, releases asbestos fibers identical to those found in nature, with no detectable alteration.[97]

Exposure to asbestos in the form of fibers is always considered dangerous. Working with, or exposure to, material that is friable, or materials or works that could cause release of loose asbestos fibers, is considered high risk. In general, people who become ill from inhaling asbestos have been regularly exposed in a job where they worked directly with the material. If Asbestos exposure occurs, individuals should speak with their GP or doctor as soon as possible.[98]

The most common diseases associated with chronic exposure to asbestos are asbestosis and mesothelioma.[99]

Regulation

Countries where asbestos is legal

United States

Researching Asbestos-Related Diseases (8743398347)
Researcher using a fiber length classifier to produce length-selected fibers of asbestos for toxological studies.

The United States remains one of the few developed countries to not ban asbestos[100] which is legal and still widely used in such commonly used products as clothing, pipeline wraps, vinyl floor tiles, millboards, cement pipes, disk brake pads, gaskets and roof coatings.[101]

In 1989 the United States Environmental Protection Agency (EPA) issued the Asbestos Ban and Phase Out Rule but in 1991, asbestos industry supporters challenged and overturned the ban in a landmark lawsuit: Corrosion Proof Fittings v. the Environmental Protection Agency. Although the case resulted in several small victories for asbestos regulation, the EPA ultimately did not put an end to asbestos use. This ruling leaves many consumer products that can still legally contain trace amounts of asbestos. For a clarification of products which legally contain asbestos, read the EPA's clarification statement.[102]

In 2010, Washington State banned asbestos in automotive brakes starting in 2014.[103] The Occupational Safety and Health Administration (OSHA), has set limits of 100,000 fibers with lengths greater than or equal to 5 µm per cubic meter of workplace air for eight-hour shifts and 40-hour work weeks.[104]

Vietnam

Wellasbestdach-233-3354 IMG
Corrugated asbestos roof (with Fibre cement)

In Vietnam, asbestos is not banned and still widely used. Vietnam is one of the top 10 asbestos users in the world with an annual import volume of about 65,000–70,000 tons of chrysotile.[105] About 90% of the imported asbestos is used to produce about 100 million m2 of roofing sheets of cement-roofing (asbestos-cement). According to one study, among 300 families in Yen Bai, Thanh Hoa, 85% of households use asbestos roofing sheets, however, only 5% know about their harms.[106]

However, in the project of adjusting the master plan for construction materials development to 2020 with orientation to 2030 submitted by the Ministry of Construction to the Government in January 2014 still suggests to continue using chrysotile for a long time.[106]

Complete bans on asbestos

Australia

SLNSW 20132 Asbestos Products Ltd exporting
Asbestos Products Ltd exporting asbestos

The use of crocidolite (blue) asbestos was banned in 1967, while the use of amosite (brown) asbestos continued in the construction industry until the mid-1980s. It was finally banned from building products in 1989, though it remained in gaskets and brake linings until 31 December 2003, and cannot be imported, used or recycled.[107][108]

Asbestos continues to be a problem. Two out of three homes in Australia built between World War II and the early 1980s still contain asbestos.[109]

The union that represents workers tasked with modifying electrical meter boxes at residences stated that workers should refuse to do this work until the boxes have been inspected for asbestos,[110] and the head of the Australian Council of Trade Unions (ACTU) has called on the government to protect its citizens by ridding the country of asbestos by 2030.[111]

Handlers of asbestos materials must have a B-Class license for bonded asbestos and an A-Class license for friable asbestos.

The town of Wittenoom, in Western Australia was built around a (blue) asbestos mine. The entire town continues to be contaminated, and has been disincorporated, allowing local authorities to remove references to Wittenoom from maps and roadsigns.

Canada

From 31 December 2018 it was illegal to import, manufacture, sell, trade or use products made from asbestos. There are exemptions for its use in the chlor-alkali industry, the military, nuclear facilities and for magnesium extraction from asbestos mining residues.[112]

Japan

Revelations that hundreds of workers had died in Japan over the previous few decades from diseases related to asbestos sparked a scandal in mid-2005.[113] Tokyo had, in 1971, ordered companies handling asbestos to install ventilators and check health on a regular basis; however, the Japanese government did not ban crocidolite and amosite until 1995, and a near complete ban with a few exceptions on asbestos was implemented in 2006, with the remaining exceptions being removed in March 2012 for a full-fledged ban.[114]

New Zealand

In 1984, the import of raw amphibole (blue and brown) asbestos into New Zealand was banned. In 2002 the import of chrysotile (white) asbestos was also banned.[115] In 2015 the government announced that the importation of asbestos would be completely banned with very limited exceptions (expected to be applied to replacement parts for older machines) that would be reviewed on a case-by-case basis.[116]

North-west of Nelson, in the Upper Takaka Valley is New Zealand's only commercially harvested asbestos mine. A low-grade Chrysotile was mined here from 1908 to 1917 but only 100 tons was washed and taken out by packhorse. A new power scheme enabled work to renew and between 1940 and 1949, 40 tons a month was mined by the Hume Company. This continued to 1964, when, due to the short length of its fibre, the limited commercial viability forced mining to cease.[117][118]

South Korea

In May 1997, the manufacture and use of crocidolite and amosite, commonly known as blue and brown asbestos, were fully banned in South Korea.[119] In January 2009, a full-fledged ban on all types of asbestos occurred when the government banned the manufacture, import, sale, storage, transport or use of asbestos or any substance containing more than 0.1% of asbestos.[120] In 2011, South Korea became the world's sixth country to enact an asbestos harm aid act, which entitles any Korean citizen to free lifetime medical care as well as monthly income from the government if he or she is diagnosed with an asbestos-related disease.[121]

United Kingdom

In the United Kingdom, blue and brown asbestos materials were banned outright in 1985 while the import, sale and second hand reuse of white asbestos was outlawed in 1999. The 2012 Control of Asbestos Regulations state that owners of non-domestic buildings (e.g., factories and offices) have a "duty to manage" asbestos on the premises by making themselves aware of its presence and ensuring the material does not deteriorate, removing it if necessary. Employers, e.g. construction companies, whose operatives may come into contact with asbestos must also provide annual asbestos training to their workers.[122]

Substitutes for asbestos in construction

Fiberglass insulation was invented in 1938 and is now the most commonly used type of insulation material. The safety of this material has also been called into question due to similarities in material structure.[123] However, the International Agency for Research on Cancer removed fiberglass from its list of possible human carcinogens in 2001[124] and a scientific review article from 2011 claimed epidemiology data was inconsistent and concluded that the IARC's decision to downgrade the carcinogenic potential of fiberglass was valid (however, this study was funded by sponsored research contract from the North American Insulation Manufacturer's Association).[125]

In 1978, a highly texturized fiberglass fabric was invented by Bal Dixit, called Zetex. This fabric is lighter than asbestos, but offers the same bulk, thickness, hand, feel, and abrasion resistance as asbestos. The fiberglass was texturized to eliminate some of the problems that arise with fiberglass, such as poor abrasion resistance and poor seam strength.[126]

In Europe, mineral wool and glass wool are the main insulators in houses.

Many companies that produced asbestos-cement products that were reinforced with asbestos fibers have developed products incorporating organic fibers. One such product was known as "Eternit" and another "Everite" now use "Nutec" fibers which consist of organic fibers, portland cement and silica. Cement-bonded wood fiber is another substitute. Stone fibers are used in gaskets and friction materials.

Another potential fiber is polybenzimidazole or PBI fiber. Polybenzimidazole fiber is a synthetic fiber with a high melting point of 760 °C (1,400 °F) that also does not ignite. Because of its exceptional thermal and chemical stability, it is often used by fire departments and space agencies.

Recycling and disposal

In most developed countries, asbestos is typically disposed of as hazardous waste in landfill sites.

The demolition of buildings containing large amounts of asbestos based materials pose particular problems for builders and property developers – such buildings often have to be deconstructed piece by piece, or the asbestos has to be painstakingly removed before the structure can be razed by mechanical or explosive means. One such example is the Red Road Flats in Glasgow, Scotland which used huge amounts of asbestos cement board for wall panelling – here British health and safety regulations stipulate that asbestos material has to be removed to a landfill site via an approved route at certain times of the day in specially adapted vehicles.

In the United States, the EPA governs the removal and disposal of asbestos strictly. Companies that remove asbestos must comply with EPA licensing. These companies are called EPA licensed asbestos contractors. Anytime one of these asbestos contractors performs work a test consultant has to conduct strict testing to ensure the asbestos is completely removed.

Asbestos can be destroyed by ultra-high-tempature incineration. A process of thermal decomposition at 1,000–1,250 °C (1,800–2,300 °F) produces a mixture of non-hazardous silicon-based wastes, and at temperatures above 1,250 °C (2,300 °F) it produces silicate glass.[127] Microwave thermal treatment can be used in an industrial manufacturing process to transform asbestos and asbestos-containing waste into porcelain stoneware tiles, porous single-fired wall tiles, and ceramic bricks.[128]

The combination of oxalic acid with ultrasound fully degrades chrysotile asbestos fibers.[129]

See also

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Bibliography

Further reading

External links

Ambler, Pennsylvania

Ambler is a borough in Montgomery County, Pennsylvania, in the United States. It is located approximately 16 miles (26 km) north of the city center of Philadelphia, Pennsylvania.

Amphibole

Amphibole ( ) is an important group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain SiO4 tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Amphiboles can be green, black, colorless, white, yellow, blue, or brown. The International Mineralogical Association currently classifies amphiboles as a mineral supergroup, within which are two groups and several subgroups.

Asbestos, Quebec

Asbestos is a town in the Estrie (Eastern Townships) region of southeastern Quebec, Canada on the Nicolet River. Asbestos is the seat of Les Sources Regional County Municipality, formerly known as the Asbestos Regional County Municipality. The town covers an area of 29.67 square kilometres (11.5 sq mi), including land acquired due to the merger of the City of Asbestos with the Municipality of Trois-Lacs on December 8, 1999.

At the 2011 census, 7,096 people resided in Asbestos. It is situated in the centre of a square formed by the cities of Drummondville, Sherbrooke and Victoriaville, and the Nicolet River to the north. It is the site of the Jeffrey mine, until recently the world's largest asbestos mine, which has long been the town's largest employer, and of the now-closed Magnola magnesium refinery. It was the site of the famous 1949 Asbestos Strike.

Asbestos Man

Asbestos Man is a fictional supervillain appearing in American comic books published by Marvel Comics. Created by editor-plotter Stan Lee, writer Ernest Hart, and artist Dick Ayers, the character first appeared in Strange Tales #111 (August 1963).

Asbestos and the law

The mineral asbestos is subject to a wide range of laws and regulations that relate to its production and use, including mining, manufacturing, use and disposal. Injuries attributed to asbestos have resulted in both workers' compensation claims and injury litigation. Health problems attributed to asbestos include asbestosis, mesothelioma, cancer, and diffuse pleural thickening.One of the major issues relating to asbestos in civil proceedings is the latency of asbestos-related diseases. Most countries have limitation periods to bar actions that are taken long after the cause of action has lapsed. For example, in Malaysia the time period to file a tort action is six years from the time the tort occurred. Due to several asbestos-related actions, countries such as Australia have amended their laws relating to limitations to accumulate starting from time of discovery rather than time when the cause of action accrued. The first employee claims for injury from exposure to asbestos in the workplace were made in 1927, and the first lawsuit against an asbestos manufacturer was filed in 1929. Since then, many lawsuits have been filed. As a result of the litigation, manufacturers sold off subsidiaries, diversified, produced asbestos substitutes, and started asbestos removal businesses.

Worldwide, 60 countries (including those in the European Union) have banned the use of asbestos, in whole or in part. It is listed as a category of controlled waste under Annex I of the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal [1992]. This means that parties to the Convention are required to prohibit the export of hazardous wastes to parties which have prohibited the import of such wastes via the notification procedure in Article 13 of the Convention. In places such as India, however, there continues to be a high use of friable or dust-based asbestos in compressed asbestos fiber (CAF) gaskets, ropes, cloth, gland packings, millboards, insulation, brake liners, and other products which are being exported without adequate knowledge and information to the other countries. Asbestos use is prevalent in India because there is no effective enforcement of the rules.

Asbestos cement

Asbestos cement, genericized as fibro or fibrolite - short for "fibrous (or fibre) cement sheet" - and AC sheet, is a building material in which asbestos fibres are used to reinforce thin rigid cement sheets.The material rose to necessity during World War II to make sturdy, inexpensive military housing, and continued to be used as an affordable substitute for many roofing products following the war. Advertised as a fireproof alternative to other roofing materials such as asphalt, asbestos-cement roofs were popular not only for safety but also for affordability. Due to asbestos-cement’s imitation of more expensive materials such as wood siding and shingles, brick, slate, and stone, the product was marketed as an affordable renovation material. Asbestos-cement faced competition with the aluminum alloy, available in large quantities after WWII, and the reemergence of wood clapboard and vinyl siding in the mid to late twentieth century.

Asbestos-cement is usually formed into flat or corrugated sheets or piping, but can be molded into any shape wet cement can fit. In Europe, many forms were historically used for cement sheets, while the US leaned more conservative in material shapes due to labor and production costs. Although fibro was used in a number of countries, it was in Australia and New Zealand where its use was the most widespread. Predominantly manufactured and sold by James Hardie & Co. until the mid-1980s, fibro in all its forms was a very popular building material, largely due to its durability. The reinforcing fibres involved in construction were almost always asbestos.

The use of fibro that contains asbestos has been banned in several countries, including Australia. As recently as 2016, the material has been discovered in new components sold for construction projects.

Asbestosis

Asbestosis is long term inflammation and scarring of the lungs due to asbestos fibres. Symptoms may include shortness of breath, cough, wheezing, and chest tightness. Complications may include lung cancer, mesothelioma, and pulmonary heart disease.Asbestosis is caused by breathing in asbestos fibers. Generally it requires a relatively large exposure over a long period of time. Such levels of exposure typically only occur in those who work with the material. All types of asbestos fibers are associated with an increased risk. It is generally recommended that currently existing asbestos be left undisturbed. Diagnosis is based upon a history of exposure together with medical imaging. Asbestosis is a type of interstitial pulmonary fibrosis.There is no specific treatment. Recommendations may include influenza vaccination, pneumococcal vaccination, oxygen therapy, and stopping smoking. Asbestosis affected about 157,000 people and resulted in 3,600 deaths in 2015. Asbestos use has been banned in a number of countries in an effort to prevent disease.

Chrysotile

Chrysotile or white asbestos is the most commonly encountered form of asbestos, accounting for approximately 95% of the asbestos in the United States and a similar proportion in other countries. It is a soft, fibrous silicate mineral in the serpentine subgroup of phyllosilicates; as such, it is distinct from other asbestiform minerals in the amphibole group. Its idealized chemical formula is Mg3(Si2O5)(OH)4. The material has physical properties which make it desirable for inclusion in building materials, but poses serious health risks when dispersed into air and inhaled.

Ferodo

Ferodo is a British brake company based in Chapel-en-le-Frith in High Peak, Derbyshire.

Fire proximity suit

A fire proximity suit (also, silvers, silver bunker suit, or asbestos suit) is a suit designed to protect a firefighter from high temperatures, especially near fires of extreme temperature such as aircraft fires. They were first designed and used in the 1930s. Originally made of asbestos fabric, current models use vacuum-deposited aluminized materials.

HMCS Asbestos

HMCS Asbestos was a Flower-class corvette that served in the Royal Canadian Navy during the Second World War. She fought primarily in the Battle of the Atlantic as a convoy escort. She was named for Asbestos, Quebec.

International Association of Heat and Frost Insulators and Allied Workers

The International Association of Heat and Frost Insulators and Allied Workers (AWIU or Insulators) is a trade union in the United States and Canada, founded in 1903. It is affiliated with the AFL–CIO and the Canadian Labour Congress and the North America's Building Trades Unions.

The union was formerly known as the International Association of Heat and Frost Insulators and Asbestos Workers, but the name was changed to reflect a symbolic new direction away from the hazards of exposure to asbestos.

James Hardie Industries

James Hardie Industries plc. is an industrial building materials company headquartered in Ireland and listed on the Australian Securities Exchange which specialises in fibre cement products. James Hardie manufactures and develops technologies, materials and processes for the production of building materials. For over 20 years, Hardie has also operated a research and development facility devoted solely to fibre-cement technology. The company was a key player in asbestos mining and manufacturing in Australia through most of the twentieth century.Working with products containing asbestos - including the building material known as Fibro or Fibrolite - caused people to develop various pleural abnormalities such as asbestosis and malignant mesothelioma. The 2009 book Killer Company and the 2012 TV docu-drama Devil's Dust are about James Hardie Industries. In May 2012 the High Court of Australia found that seven former James Hardie non-executive directors misled the stock exchange over the asbestos victims compensation fund.

Johns Manville

Johns Manville is an American corporation based in Denver, Colorado that manufactures insulation, roofing materials, and engineered products. For much of the 20th century, the then-titled Johns-Manville Corporation was the global leader in the manufacture of asbestos-containing products, including asbestos pipe insulation, asbestos shingles, asbestos roofing materials and asbestos cement pipe.Johns Manville stock was included in the Dow Jones Industrial Average from January 29, 1930 to August 27, 1982 when it was replaced by American Express. In 1981, Johns-Manville Corporation was renamed simply "Manville". In 1982, facing unprecedented liability for asbestos injury claims, Johns Manville voluntarily filed for bankruptcy under Chapter 11 of the U.S. Bankruptcy Code.Berkshire Hathaway bought the company in 2001. Chairman and CEO Jerry Henry retired in 2004; Steve Hochhauser became chairman, president and CEO. Todd Raba succeeded him in the summer of 2007; Raba came from MidAmerican Energy Holdings, another Berkshire Hathaway company. In November 2012, Mary Rhinehart was named president and CEO.

Mesothelioma

Mesothelioma is a type of cancer that develops from the thin layer of tissue that covers many of the internal organs (known as the mesothelium). The most common area affected is the lining of the lungs and chest wall. Less commonly the lining of the abdomen and rarely the sac surrounding the heart, or the sac surrounding the testis may be affected. Signs and symptoms of mesothelioma may include shortness of breath due to fluid around the lung, a swollen abdomen, chest wall pain, cough, feeling tired, and weight loss. These symptoms typically come on slowly.More than 80% of mesothelioma cases are caused by exposure to asbestos. The greater the exposure the greater the risk. As of 2013, about 125 million people worldwide have been exposed to asbestos at work. High rates of disease occur in people who mine asbestos, produce products from asbestos, work with asbestos products, live with asbestos workers, or work in buildings containing asbestos. Asbestos exposure and the onset of cancer are generally separated by about 40 years. Washing the clothing of someone who worked with asbestos also increases the risk. Other risk factors include genetics and infection with the simian virus 40. The diagnosis may be suspected based on chest X-ray and CT scan findings, and is confirmed by either examining fluid produced by the cancer or by a tissue biopsy of the cancer.Prevention centers around reducing exposure to asbestos. Treatment often includes surgery, radiation therapy, and chemotherapy. A procedure known as pleurodesis, which involves using substances such as talc to scar together the pleura, may be used to prevent more fluid from building up around the lungs. Chemotherapy often includes the medications cisplatin and pemetrexed. The percentage of people that survive five years following diagnosis is on average 8% in the United States.In 2015, about 60,800 people had mesothelioma, and 32,000 died from the disease. Rates of mesothelioma vary in different areas of the world. Rates are higher in Australia, the United Kingdom, and lower in Japan. It occurs in about 3,000 people per year in the United States. It occurs more often in males than females. Rates of disease have increased since the 1950s. Diagnosis typically occurs after the age of 65 and most deaths occur around 70 years old. The disease was rare before the commercial use of asbestos.

Richmond—Arthabaska

Richmond—Arthabaska is a federal electoral district in Quebec, Canada, that has been represented in the House of Commons of Canada since 1997.

Serpentine subgroup

The serpentine subgroup (part of the kaolinite-serpentine group) are greenish, brownish, or spotted minerals commonly found in serpentinite rocks. They are used as a source of magnesium and asbestos, and as a decorative stone. The name is thought to come from the greenish color being that of a serpent.The serpentine group describes a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals, resulting from the metamorphism of the minerals that are contained in ultramafic rocks. They may contain minor amounts of other elements including chromium, manganese, cobalt or nickel. In mineralogy and gemology, serpentine may refer to any of 20 varieties belonging to the serpentine group. Owing to admixture, these varieties are not always easy to individualize, and distinctions are not usually made. There are three important mineral polymorphs of serpentine: antigorite, chrysotile and lizardite.

The serpentine group of minerals are polymorphous, meaning that they have the same chemical formulae, but the atoms are arranged into different structures, or crystal lattices. Chrysotile, which has a fiberous habit, is one polymorph of serpentine and is one of the more important asbestos minerals. Other polymorphs in the serpentine group may have a platy habit. Antigorite and lizardite are the polymorphs with platy habit.

Many types of serpentine have been used for jewellery and hardstone carving, sometimes under the name false jade or Teton jade.

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

Vermiculite

Vermiculite is a hydrous phyllosilicate mineral. It undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently, and the effect is routinely produced in commercial furnaces. Vermiculite is formed by weathering or hydrothermal alteration of biotite or phlogopite. Large commercial vermiculite mines currently exist in Russia, South Africa, China, and Brazil.

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