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| {{Distinguish|Chrysolite}}
| | My name is Kerstin and I am studying International Relations and Business at Trosa / Sweden.<br><br>Also visit my site :: Hostgator 1 cent coupon ([http://multimisiekpl.cba.pl/?author=7815 http://multimisiekpl.cba.pl/]) |
| {{Infobox mineral
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| | name = Chrysotile
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| | category = [[Phyllosilicates]] <br />Kaolinite-[[serpentine group]]
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| | boxwidth = 200px
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| | image = Chrysotile.jpg
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| | caption = Chrysotile serpentine from the [[Salt River (Arizona)|Salt River]] area, [[Arizona]]
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| | formula = [[Magnesium|Mg]]{{sub|3}}([[Silicon|Si]]{{sub|2}}[[Oxygen|O]]{{sub|5}})([[Hydroxide|OH]]){{sub|4}}<br/>(''ideal'')
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| | strunz = 09.ED.15
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| | molweight = 277.11 g/mol<br/>(''ideal'')
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| | color = grey to green
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| | habit = acicular
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| | system = [[monoclinic]] or [[orthorhombic]]
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| | twinning =
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| | cleavage =
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| | fracture = fibrous
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| | tenacity =
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| | mohs = 2½–3
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| | luster = silky
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| | polish =
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| | refractive = 1.545–1.569; 1.553–1.571
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| | opticalprop =
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| | birefringence = 0.008 (max)
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| | dispersion = relatively weak
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| | pleochroism =
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| | fluorescence=
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| | absorption =
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| | streak = white
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| | gravity =
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| | density = 2.53 g/ml
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| | melt =
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| | fusibility = [[Dehydration (chemistry)|dehydrates]] at 550–750 °C
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| | diagnostic =
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| | solubility = insoluble in water<br/>fibres degrade in dilute acid
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| | diaphaneity = translucent
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| | other =
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| | references =
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| }}
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| '''Chrysotile''' or '''white asbestos''' is the most commonly encountered form of [[asbestos]],<ref name="11thRoC">[[United States Department of Health and Human Services|U.S. Department of Health and Human Services]] (2005). "[http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s016asbe.pdf Asbestos]." ''[http://ntp.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E-7FCE50709CB4C932# Report on Carcinogens, Eleventh Edition].''</ref> accounting for approximately 95% of the asbestos in place in the United States<ref name="29CFR1910J">[[Occupational Safety and Health Administration]], [[United States Department of Labor|U.S. Department of Labor]] (2007). [http://edocket.access.gpo.gov/cfr_2007/julqtr/pdf/29cfr1910.1001.pdf 29 C.F.R. 1910.1001]. Appendix J.</ref> and a similar proportion in other countries.<ref name="INRS">[[Institut national de recherche sur la sécurité]] (1997). "[http://www.inrs.fr/inrs-pub/inrs01.nsf/IntranetObject-accesParReference/FT%20145/$File/ft145.pdf Amiante]." ''Fiches toxicologiques.'' n° 167. (in French)</ref> It is a soft, fibrous [[silicate mineral]] in the [[serpentine group]] of [[phyllosilicate]]s; as such, it is distinct from other asbestiform minerals in the [[amphibole group]]. Its idealized [[chemical formula]] is [[Magnesium|Mg]]{{sub|3}}([[Silicon|Si]]{{sub|2}}[[Oxygen|O]]{{sub|5}})([[Hydroxide|OH]]){{sub|4}}.<ref name="11thRoC"/>
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| == Polytypes==
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| Three [[polytype]]s of chrysotile are known.<ref>{{cite journal |url=http://canmin.geoscienceworld.org/cgi/content/abstract/13/3/227 |journal=The Canadian Mineralogist |volume=13 |year=1975 |pages=227–243 |title=A reappraisal of the structures of the serpentine minerals |first1=F. J. |last1=Wicks |first2=E. J. W. |last2=Whittaker |issue=3}}</ref> These are very difficult to distinguish in hand specimens, and [[polarized light]] [[microscopy]]<ref name="29CFR1910J"/> must normally be used. Some older publications refer to chrysotile as a group of minerals—the three polytypes listed below, and sometimes [[pecoraite]] as well—but the 2006 recommendations of the [[International Mineralogical Association]] prefer to treat it as a single mineral with a certain variation in its naturally-occurring forms.<ref>{{cite journal |last1=Burke |first1=Ernst A. J. |title=A Mass Discreditation of GQN Minerals |journal=The Canadian Mineralogist |volume=44 |issue=6 |pages=1557–60 |year=2006 |doi=10.2113/gscanmin.44.6.1557 |url=http://pubsites.uws.edu.au/ima-cnmnc/GQNminerals.pdf}}</ref>
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| {| class="wikitable"
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| |-
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| ! Name
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| ! [[Crystal system]]
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| ! [[Type locality (geology)|Type locality]]
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| ! [[mindat.org]] reference
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| ! [[Unit cell]] parameters
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| ! Crystal structure reference
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| |-
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| | Clinochrysotile
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| | [[monoclinic]]
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| | [[Złoty Stok]]*, [[Lower Silesia]], [[Poland]]
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| | <span class="reflink plainlinksneverexpand">[http://www.mindat.org/min-1071.html 1071]</span>
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| | ''a'' = 5.3 Å; ''b'' = 9.19 Å; ''c'' = 14.63 Å; β = 93°
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| | <ref>{{cite journal |last1=Whittaker |first1=E. J. W. |title=The structure of chrysotile. II. Clino-chrysotile |journal=Acta Crystallographica |volume=9 |pages=855–62 |year=1956 |doi=10.1107/S0365110X5600245X |issue=11}}</ref>
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| |-
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| | Orthochrysotile
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| | [[orthorhombic]]
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| | [[Kadapa district|Kadapa* district]], [[Andhra Pradesh]], [[India]]
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| | <span class="reflink plainlinksneverexpand">[http://www.mindat.org/min-3025.html 3025]</span>
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| | ''a'' = 5.34 Å; ''b'' = 9.24 Å; ''c'' = 14.2 Å
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| | <ref>{{cite journal |last1=Whittaker |first1=E. J. W. |title=The structure of chrysotile. III. Ortho-chrysotile |journal=Acta Crystallographica |volume=9 |pages=862–64 |year=1956 |doi=10.1107/S0365110X56002461 |issue=11}}</ref>
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| |-
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| | Parachrysotile
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| | [[orthorhombic]]
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| | uncertain
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| | <span class="reflink plainlinksneverexpand">[http://www.mindat.org/min-3083.html 3083]</span>
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| | ''a'' = 5.3 Å; ''b'' = 9.24 Å; ''c'' = 14.71 Å
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| | <ref>{{cite journal |last1=Whittaker |first1=E. J. W. |title=The structure of chrysotile. IV. Para-chrysotile |journal=Acta Crystallographica |volume=9 |pages=865–67 |year=1956 |doi=10.1107/S0365110X56002473 |issue=11}}</ref>
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| |-
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| | colspan=6 | <small>''Source'': [[mindat.org]].<br/>*Złoty Stok and Kadapa have formerly been known as Reichenstein and Cuddapah respectively, and these names may appear in some publications.</small>
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| |}
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| Clinochrysotile is the most common of the three forms, found notably at [[Asbestos, Quebec]], [[Canada]]. Its two measurable [[Refractive index|refractive indices]] tend to be lower than those of the other two forms.<ref>In principle, all polytypes of chrysotile should have three independent refractive indices: in practice, two of the three are so close as to be indistinguishable by experimental measurement.</ref> The orthorhombic paratypes may be distinguished by the fact that, for orthochrysotile, the higher of the two observable refractive indices is measured parallel to the long axis of the fibres (as for clinochrysotile); whereas for parachrysotile the higher refractive index is measured perpendicular to the long axis of the fibres.
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| == Physical properties ==
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| [[File:Chrysotile SEM photo.jpg|left|thumb|SEM photo of Chrysotile.]]
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| Bulk chrysotile, whose hardness is about the same as that of a human [[fingernail]], is easily crumbled to fibres that are, in fact, bundles of fibrils. Naturally-occurring fibre bundles range in length from several millimetres to more than ten centimetres,<ref name="11thRoC"/> although industrially-processed chrysotile usually has shorter fibre bundles. The diameter of the fibre bundles is 0.1–1 [[micrometre|µm]], and the individual fibrils are even finer, 0.02–0.03 µm, each fibre bundle containing tens or hundreds of fibrils.<ref name="INRS"/>
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| Chrysotile fibres have considerable tensile strength, and may be spun into thread and woven into cloth. They are also resistant to heat and are excellent thermal, electrical and acoustic insulators.<ref name="11thRoC"/><ref name="INRS"/>
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| == Chemical properties ==
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| The idealized [[chemical formula]] of chrysotile is [[Magnesium|Mg]]{{sub|3}}([[Silicon|Si]]{{sub|2}}[[Oxygen|O]]{{sub|5}})([[Hydroxide|OH]]){{sub|4}}, although some of the [[magnesium]] ions may be replaced by [[iron]] or other cations. Substitution of the [[hydroxide]] ions for [[fluoride]], [[oxide]] or [[chloride]] is also known, but rarer.<ref name="11thRoC"/> A related, but much rarer, mineral is [[pecoraite]], in which all the magnesium cations of chrysotile are substituted by [[nickel]] cations.
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| Chrysotile is resistant to even strong bases (asbestos is thus stable in high pH pore water of Portland [[cement]]), but the fibres are attacked by acids: the magnesium ions are selectively dissolved, leaving a [[silica]] skeleton. It is thermally stable up to around 550 °C, at which temperature it starts to [[Dehydration (chemistry)|dehydrate]]. Dehydration is complete at about 750 °C, with the final products being [[forsterite]] (magnesium silicate), silica and water.<ref name="INRS"/>
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| The global mass balance reaction of the chrysotile dehydration can be written as follows: <br />
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| :''Chrysotile (serpentine) → Forsterite + silica + water'' | |
| :<math>\mathrm{2Mg_3Si_2O_5(OH)_4}</math> → <math>\mathrm{3Mg_2SiO_4 + SiO_2 + 4H_2O}</math> | |
| The chrysotile (serpentine) dehydration reaction corresponds to the reverse of the forsterite (Mg-[[olivine]]) hydrolysis in the presence of dissolved [[silica]] ([[silicic acid]]).
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| == Safety concerns ==
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| [[Image:Asbestos1USGOV.jpg|thumb|Chrysotile asbestos]]
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| Chrysotile has been included with other forms of [[asbestos]], in being considered to be a human [[carcinogen]] by the [[International Agency for Research on Cancer]] (IARC)<ref name="IARCs7">[[International Agency for Research on Cancer]] (1998). "Asbestos." However, the study states " In some of these case reports and in other studies, asbestos fibres have been identified in the lung. Amphibole fibres have usually predominated, but in a few cases mainly or only chrysotile fibres were found." ''[http://monographs.iarc.fr/ENG/Monographs/suppl7/suppl7.pdf IARC Monographs on Evaluating the Carcinogenic Risks to Humans. Supplement 7].''</ref> and by the [[United States Department of Health and Human Services|U.S. Department of Health and Human Services]].<ref name="11thRoC"/> These state that "Asbestos exposure is associated with [[Asbestosis|parenchymal asbestosis]], asbestos-related [[Pleural cavity|pleural]] abnormalities, [[peritoneal mesothelioma]], and [[lung cancer]], and it may be associated with cancer at some extra-[[Chest|thoracic]] sites".<ref name="ATSDR">[[Agency for Toxic Substances and Disease Registry]] (ATDSR), [[United States Department of Health and Human Services|U.S. Department of Health and Human Services]] (2007). "[http://www.atsdr.cdc.gov/csem/asbestos/cover2.html Asbestos Toxicity]." ''Case Studies in Environmental Medicine.''</ref> In other scientific publications, epidemiologists have published peer reviewed scientific papers establishing that chrysotile is the main cause of [[pleural mesothelioma]].<ref>[http://asrg.berkeley.edu/96SmithChrysotile.pdf] See e.g., Smith, Allen "Chrysotile is the main cause of pleural mesothelioma", Amer.J.Indus.Med., Vol. 32, pp. 252 to 266 (1996)</ref><ref>[http://www.sjweh.fi/show_abstract.php?abstract_id=226] Tossavainen A, "Asbestos, asbestosis, and cancer: the Helsinki criteria for diagnosis and attribution" Scand J Work Environ Health 1997;23(4):311–316 (stating that all types of malignant mesothelioma can be induced by asbestos, with the amphiboles showing greater carcinogenic potency than chrysotile)</ref><ref>[http://dx.doi.org/10.1289/ehp.1002446] Lemen RA 2010. Chrysotile Asbestos and Mesothelioma. Environ Health Perspect 118:a282-a282</ref>
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| Chrysotile has been recommended for inclusion in the [[Rotterdam Convention|Rotterdam Convention on Prior Informed Consent]],<ref>[http://www.pic.int/TheConvention/Chemicals/Recommendedforlisting/Chrysotileasbestos/tabid/1186/language/en-US/Default.aspx Rotterdam Convention: Chrysotile]</ref> an international treaty that restricts the global trade in hazardous materials. If listed, exports of chrysotile would only be permitted to countries that explicitly consent to imports. [[Canada]], a major producer of the mineral, has been harshly criticized by the [[Canadian Medical Association]]<ref name="pmid18936444">{{cite journal |first1=Amir |last1=Attaran |first2=David R. |last2=Boyd |first3=Matthew B. |last3=Stanbrook |title=Asbestos mortality: a Canadian export |journal=CMAJ |volume=179 |issue=9 |pages=871–2 |date=October 2008 |pmid=18936444 |pmc=2565724 |doi=10.1503/cmaj.081500}}</ref><ref>{{cite journal |last=Collier |first=Roger |date=December 2008 |title=Health advocates assail Canada's asbestos stance |volume=179 |issue=12 |pmid=19047602 |doi=10.1503/cmaj.081806 |pages=1257 |pmc=2585122 |journal=CMAJ}}</ref> for its opposition to including chrysotile in the Convention.<ref>{{cite news|url=http://www.theglobeandmail.com/servlet/Page/document/v5/content/subscribe?user_URL=http://www.theglobeandmail.com%2Fservlet%2Fstory%2FLAC.20080910.ASBESTOS10%2FTPStory%2FNational&ord=87597914&brand=theglobeandmail&force_login=true|title=Canada still blocking action on asbestos|last=MITTELSTAEDT|first=MARTIN|date=September 10, 2008|accessdate=2008-10-01|location=Toronto|work=The Globe and Mail}}</ref>
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| ==Critics of safety regulations==
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| ===1990s: Canada-European dispute GATT dispute===
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| In May 1998, Canada requested consultations before the [[WTO]] and the [[European Commission]] concerning France's 1996 prohibition of the importation and sale of all forms of asbestos. Canada said that the French measures contravened provisions of the [[Phytosanitary|Agreements on Sanitary and Phytosanitary Measures]] and on Technical Barriers to Trade, and the [[GATT]] 1994. The EC claimed that safer substitute materials existed to take the place of asbestos. It stressed that the French measures were not discriminatory under the terms of international trade treaties, and were fully justified for public health reasons. The EC further claimed that in the July consultations, it had tried to convince Canada that the measures were justified, and that just as Canada broke off consultations, it (the EC) was in the process of submitting substantial scientific data in favour of the asbestos ban.<ref name="wto">[http://www.wto.org/english/news_e/news98_e/wdsboct.htm EC measures affecting asbestos products]. World Trade Organization News. 29 October 1998</ref>
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| ===2000s: Canadian exports face mounting global criticism===
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| In the late 1990s and early 2000s, the Canadian federal government continued to claim that chrysotile was much less dangerous than other types of asbestos.<ref>{{cite news |title=Canada diminished by asbestos hypocrisy |first=Tim |last=Harper |date=3 July 2011 |work=[[The Chronicle Herald]] |url=http://asbestosexposuresymptoms.us/2011/07/03/canada-diminished-by-asbestos-hypocrisy/}}</ref> Chrysotile continued to be used in new construction across Canada, in ways that are very similar to those for which chrysotile was exported.<ref name="Asbestos is safe when handled properly">{{cite news |title=Asbestos is safe when handled properly |first=Guy |last=Versailles |date=5 July 2011 |url=http://www.montrealgazette.com/health/Asbestos+safe+when+handled+properly/5055153/story.html |work=The Montreal Gazette}} {{dead link|date=January 2012}}</ref> Similarly, Natural Resources Canada once stated that chrysotile, one of the fibres that make up asbestos, was not as dangerous as once thought. According to a fact sheet from 2003, "current knowledge and modern technology can successfully control the potential for health and environmental harm posed by chrysotile".<ref>{{cite web |url=http://www.nrcan.gc.ca/mms/pdf/chry_e.pdf |title=Chrysolite Asbestos Fact Sheet |publisher=Natural Resources Canada |date=3 February 2009 |accessdate=2010-01-12}} {{dead link|date=January 2012}}</ref> The Chrysotile Institute, an association partially funded by the Canadian government, also prominently asserted that the use of chrysotile did not pose an environmental problem and the inherent risks in its use were limited to the workplace.<ref>{{cite news |title=NDP MP Martin's one-man battle to ban asbestos mining in Canada gains traction |first=Bea |last=Vongdouangchanh |date=5 July 2011 |work=The Hill Times |url=http://www.hilltimes.com/news/2011/07/05/ndp-mp-martins-one-man-battle-to-ban-asbestos-mining-in-canada-gains-traction/27900}}</ref>
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| However, under increasing criticism by environmental groups, in May, 2012, the Canadian government stopped funding the Chrysotile Institute.<ref>[http://www.montrealgazette.com/health/asbestos+advocacy+group+shuts+doors/6537818/story.html Asbestos Advocacy Group Shuts Its Doors, Montreal Gazette]</ref><ref>[http://www.cancer.ca/Canada-wide/About%20us/Media%20centre/CW-Media%20releases/CW-2011/Chrysotile%20Institute%20Funding.aspx?sc_lang=en Canadian Cancer Society Disappointed with Proposed Federal Government Funding for Chrysotile Institute, 3 March 2012]</ref> As a result, the Chrysotile Institute has now closed.<ref>[http://www.themadskeptic.com/ R.I.P. Chrysotile Institute, The Mad Scientist Blog]></ref><ref>[http://www.vancouversun.com/health/asbestos+advocacy+group+shuts+doors/6537818/story.html Asbestos Advocacy Group Shuts Its Doors, Vancouver Sun, 29 April 2012]</ref><ref>[http://www.sierraclub.ca/en/trade-and-environment/publications/minister-flaherty-stop-funding-chrysotile-institute "Minister Flaherty: Stop Funding The Chrysotile Institute", 2 Feb. 2011]</ref>
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| The Canadian government continues to draw both domestic and international criticism for its stance on chrysotile, most recently in international meetings about the [[Rotterdam Convention]] hearings regarding chrysotile. The [[Construction, Forestry, Mining and Energy Union|CFMEU]] pointed out that most exports go to developing countries. Canada has pressured countries, including [[Chile]], and other UN member states to avoid chrysotile bans.<ref>[http://www.cfmeu-construction-nsw.com.au/tacanadianasbestos.htm Stop Canada's Export Of Asbestos] CFMEU{{dead link|date=January 2012}}</ref> In November, 2011, the Australian Upper House passed a motion to pressure the Canadian government to end policies supporting asbestos exports.<ref>[http://www.themarknews.com/news/?open=7487 Australian Senate Slams Canada's Asbestos Industry, 17 November 2011]</ref>
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| In September 2012, governments in Quebec and Canada ended official support for Canada's last asbestos mine in [[Asbestos, Quebec]].<ref>{{cite news |title=Canada axes support for asbestos mining |date=17 Oct 2012 |author=Daniel Lak |work=Al Jazeera |url=http://www.aljazeera.com/indepth/features/2012/10/201210167129546890.html}}</ref>
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| ==See also==
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| * [[Serpentinite#Serpentinite_reactions|Serpentinite reactions]]
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| ==References==
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| {{Reflist}}
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| ==External links==
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| *[http://www.chrysotile.com/ The Chrysotile Institute]
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| *{{ICSC|0014|00}}
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| *[http://webmineral.com/data/Chrysotile.shtml Webmineral]
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| *[http://www.mindat.org/min-1071.html Mindat clinochrysotile]
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| *[http://www.mindat.org/min-3025.html Mindat orthochrysotile]
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| *[http://www.mindat.org/min-3083.html Mindat parachrysotile]
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| *[http://ibe.sagepub.com/cgi/content/abstract/14/1/83 "Asbestos-containing Floor Tile and Mastic Abatement: Is there Enough Exposure to Cause Asbestos-related Disease?"]
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| *Deer William Alexander, Howie Robert Andrew, Zussman Jack, ''[[An introduction to the rock-forming minerals]]'', ISBN 0-582-30094-0, OCLC 183009096 pp. 344–352, 1992
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| *Ledoux, RL (ed), ''Short course in mineralogical techniques of asbestos determination'', Mineralogical Association of Canada, pp. 35–73, 185, 1979.
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| *http://www.microlabgallery.com/ChrysotileFile.aspx Photomicrographs of parachrysotile and clinochrysotile
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| *Nolan, RP, Langer AM, Ross M, Wicks FJ, Martin RF (eds), "The health effects of chrysotile asbestos", ''The Canadian Mineralogist'', Special Publication 5, 2001.
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| {{Phyllosilicates}}
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| [[Category:Serpentine group]]
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| [[Category:Magnesium minerals]]
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| [[Category:Asbestos]]
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| [[Category:IARC Group 1 carcinogens]]
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