Талк — разлика између измена

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{{short description|Hydrated magnesium phyllosilicate mineral}}{{рут}}
{{Infobox mineral
| name = Талк = Талк
| category = [[Silicate mineral|Силикатни = минерал]]
| boxwidth =
| boxbgcolor = #aad595
| image= = Talc-177589.jpg
| imagesize = 260px
| caption = Кристали талка
| caption =
| formula = -{[[Магнезијум|Mg]]<sub>3</sub>[[Силицијум|Si]]<sub>4</sub>[[Кисеоник|O]]<sub>10</sub>([[Хидроксид|OH]])<sub>2</sub>}-
| formula = Mg<sub>3</sub>Si<sub>4</sub>O<sub>10</sub>(OH)<sub>2</sub>
| molweight =
| IMAsymbol = Tlc<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616}}</ref>
| color = бео до сив или зелен
| system = [[Monoclinic]] or [[triclinic]]<ref name="DHZ">''[[An Introduction to the Rock-Forming Minerals]]'', 2 ed., by [[William Alexander Deer|W.A. Deer]], R.A. Howie, and J. Zussman, 1992, Prentice Hall, {{ISBN|0-582-30094-0}}.</ref>
| habit = листасте до влакнастих маса
| class = Either prismatic (2m) or pinacoidal ({{overline|1}})<ref name=Handbook/>
| system = [[Моноклиничан]]
| symmetry = ''C2/c'' or ''C{{overline|1}}''
| twinning =
| unit cell = a = 5.291&nbsp;[[Ångström|Å]], b = 9.173&nbsp;Å<br />c = 5.290&nbsp;Å; α = 98.68°<br />β = 119.90°, γ = 90.09°; Z&nbsp;=&nbsp;2 or<br />a = 5.287&nbsp;Å, b = 9.158&nbsp;Å<br />c = 18.95&nbsp;[Å], β = 99.3°; Z&nbsp;=&nbsp;4<ref name=Handbook/>
| cleavage = перфектна [[калавост]]
| fracture strunz = 9.EC.05
| color = Light to dark green, brown, white, grey, colorless
| mohs = 1
| habit = Foliated to fibrous masses, rare as platey to pyramidal crystals
| luster = воскаста или бисерна
| refractive twinning =
| cleavage = Perfect on {001} [[Cleavage (crystal)|basal cleavage]]
| opticalprop =
| fracture = Flat surfaces (not cleavage), fracture in an uneven pattern
| birefringence =
| tenacity = [[Sectility|Sectile]]
| pleochroism =
| mohs = 1 (defining mineral)
| streak = Бео
| luster = Waxlike or pearly
| gravity = 2,5-2,8
| refractive = n<sub>α</sub> = 1.538 – 1.550<br />n<sub>β</sub> = 1.589 – 1.594<br />n<sub>γ</sub> = 1.589 – 1.600
| melt =
| opticalprop = Biaxial (-)
| fusibility =
| diagnosticbirefringence = δ = 0.051
| pleochroism = Weak in dark varieties
| solubility =
| streak = White jot to pearl black
| diaphaneity =
| othergravity = 2.58 to = 2.83
| melt =
| fusibility =
| diagnostic =
| solubility =
| diaphaneity = Translucent
| fluorescence = Short UV=orange yellow, long UV=yellow
| references = <ref name=Handbook>{{cite book|editor1=Anthony, John W. |editor2=Bideaux, Richard A. |editor3=Bladh, Kenneth W. |editor4=Nichols, Monte C. |title= Handbook of Mineralogy|publisher= Mineralogical Society of America|place= Chantilly, VA, US|chapter-url=http://rruff.geo.arizona.edu/doclib/hom/talc.pdf|chapter=Talc|isbn=0962209716 |volume=II (Silica, Silicates)|year=1995}}</ref><ref name=Mindat>[http://www.mindat.org/min-3875.html Talc]. Mindat.org</ref><ref name=Webmin>[http://webmineral.com/data/Talc.shtml Talc]. Webmineral</ref>
}}
 
[[Датотека:Talcum Powder.JPEG|мини|Талков прах]]
'''Талк''' (изведено из персијског преко арапског -{''talq''}-) је [[минерал]] по саставу [[хидрат]]исани [[магнезијум]] [[силикат]] формуле -{[[Водоник|H]]<sub>2</sub>[[Магнезијум|Mg]]<sub>3</sub>([[Силикат|SiO]]<sub>3</sub>)<sub>4</sub>}- или -{Mg<sub>3</sub>[[Силицијум|Si]]<sub>4</sub>[[Кисеоник|O]]<sub>10</sub>([[Хидроксид|OH]])<sub>2</sub>}-. Talc in powdered form, often combined with [[corn starch]], is used as [[baby powder]]. This mineral is used as a thickening agent and lubricant. It is an ingredient in ceramics, paint, and roofing material. It is a main ingredient in many cosmetics.<ref>{{cite web |title=Talc |url=https://mineralseducationcoalition.org/minerals-database/talc/ |website=Minerals Education Coalition}}</ref> It occurs as [[Foliation (geology)|foliated]] to [[Fiber|fibrous]] masses, and in an exceptionally rare [[crystal]] form. It has a perfect [[cleavage (crystal)|basal cleavage]] and an uneven flat fracture, and it is foliated with a two-dimensional platy form.
 
The [[Mohs scale of mineral hardness]], based on [[Scratch hardness|scratch]] [[hardness comparison]], defines value 1 as the hardness of talc, the softest mineral. When scraped on a [[streak (mineralogy)|streak plate]], talc 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 [[Lustre (mineralogy)|luster]]. Talc is not soluble in water, and is slightly soluble in dilute [[mineral acid]]s.<ref>''Profiles of Drug Substances, Excipients and Related Methodology, Volume 36'' {{ISBN|978-0-123-87667-6}} p. 283</ref>
 
== Настанак ==
[[Датотека:Talcum Powder.JPEG|мини|250п|лево|Талков прах]]
[[Датотека:Talc block.jpg|thumb|лево|Блок талка]]
 
Талк је матаморфни минерал, дакле настаје метаморфозом магнезијумових минерала, као што су [[пироксени|пироксен]], [[амфибол]] [[оливин]] и други слични минерали, у присуству угљендиоксида и воде. Процес је познат као ''карбонизација талка'' или ''стеатизација'' њим настаје читава серија стена познатих као талкови карбонати.
 
Талк првенствено настаје хидратацијом и карбонизацијом [[серпентин]]а, по следећој реакцији:
 
:{{overset|[[Serpentine subgroup|Серпентин]]|2 Mg<sub>3</sub>Si<sub>2</sub>O<sub>5</sub>(OH)<sub>4</sub>}} + {{overset|[[угљен-диоксид]]|3 CO<sub>2</sub>}} → {{overset|talc|Mg<sub>3</sub>Si<sub>4</sub>O<sub>10</sub>(OH)<sub>2</sub>}} + {{overset|[[магнезит]]|3 MgCO<sub>3</sub>}} + {{overset|[[вода]]|3 H<sub>2</sub>O}}
''[[Серпентин]] + [[Угљен-диоксид|Угљендиоксид]] → Талк + [[Магнезит]] + [[Вода]]''
 
:<math>2Mg_3Si_2O_5(OH)_4 + 3CO_2 \rarr Mg_3Si_4O_{10}(OH)_2 + 3MgCO_3 + 3H_2O</math>
Талк такође може да настане у реакцији доломита и силицијумдиоксида, which is typical of [[skarn]]ification of dolomites by silica-flooding in contact metamorphic aureoles:
 
:{{overset|[[Dolomite (mineral)|Доломит]]|3 CaMg(CO<sub>3</sub>)<sub>2</sub>}} + {{overset|[[силицијум диоксид]]|4 SiO<sub>2</sub>}} + {{overset|water|H<sub>2</sub>O}} → {{overset|talc|Mg<sub>3</sub>Si<sub>4</sub>O<sub>10</sub>(OH)<sub>2</sub>}} + {{overset|[[калцит]]|3 CaCO<sub>3</sub>}} + {{overset|carbon dioxide|3 CO<sub>2</sub>}}
 
Talc can also be formed from magnesian chlorite and quartz in [[blueschist]] and [[eclogite]] metamorphism by the following [[metamorphic reaction]]:
: ''[[Хлорит]] + [[Кварц]] → [[Кијанит]] + Талк + -{H}-<sub>2</sub>O''
 
Talc is also found as a diagenetic mineral in sedimentary rocks where it can form from the transformation of metastable hydrated magnesium-clay precursors such as [[kerolite]], [[sepiolite]], or [[stevensite]] that can precipitate from marine and lake water in certain conditions.<ref name="Strauss MacDonald Halverson Tosca 2015 pp. 881–944">{{cite journal | last1=Strauss | first1=Justin V. | last2=MacDonald | first2=Francis A. | last3=Halverson | first3=Galen P. | last4=Tosca | first4=Nicholas J. | last5=Schrag | first5=Daniel P. | last6=Knoll | first6=Andrew H. | title=Stratigraphic evolution of the Neoproterozoic Callison Lake Formation: Linking the break-up of Rodinia to the Islay carbon isotope excursion | journal=American Journal of Science | publisher=American Journal of Science (AJS) | volume=315 | issue=10 | year=2015 | issn=0002-9599 | doi=10.2475/10.2015.01 | pages=881–944| bibcode=2015AmJS..315..881S | s2cid=130671089 | url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:30367434 }}</ref>
 
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#Blueschist facies|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.<ref name="DHZ" /> The crystal structure of talc is described as ''TOT'', meaning that it is composed of parallel ''TOT'' layers weakly bonded to each other by weak [[van der Waals force]]s. The ''TOT'' layers in turn consist of two tetrahedral sheets (''T'') strongly bonded to the two faces of a single trioctahedral sheet (''O''). It is the weak bonding between ''TOT'' layers that gives talc its perfect basal cleavage and softness.{{sfn|Nesse|2000|p=238}}
 
The tetrahedral sheets consist of silica tetrahedra, which are silicon ions surrounded by four oxygen ions. The tetrahedra each share three of their four oxygen ions with neighboring tetrahedra to produce a hexagonal sheet. The remaining oxygen ion (the ''apical'' oxygen ion) is available to bond with the trioctahedral sheet.{{sfn|Nesse|2000|p=235}}
 
The trioctahedral sheet has the structure of a sheet of the mineral [[brucite]]. Apical oxygens take the place of some of the hydroxyl ions that would be present in a brucite sheet, bonding the tetrahedral sheets tightly to the trioctahedral sheet.{{sfn|Nesse|2000|pp=235-237}}
 
Tetrahedral sheets have a negative charge, since their bulk composition is Si<sub>4</sub>O<sub>10</sub><sup>4-</sup>. The trioctahedral sheet has a equal positive charge, since its bulk composition is Mg<sub>3</sub>(OH)<sub>2</sub><sup>4+</sup> The combined TOT layer thus is electrically neutral.{{sfn|Nesse|2000|p=238}}
 
Because the hexagons in the T and O sheets are slightly different in size, the sheets are slightly distorted when they bond into a TOT layer. This breaks the hexagonal symmetry and reduces it to monoclinic or triclinic symmetry.{{sfn|Nesse|2000|p=239,242}} However, the original hexahedral symmetry is discernible in the pseudotrigonal character of talc crystals.<ref name=Handbook/>
 
<gallery widths="250px" heights="180px">
File:Mica T.png|View of tetrahedral sheet structure of talc. The apical oxygen ions are tinted pink.
File:Talc to.jpg|thumb|View of trioctahedral sheet of talc. Yellow spheres are hydroxyl; blue are magnesium. Apical oxygen binding sites are white.
File:Talc structure.jpg|thumb|Talc crystal viewed along the [100] axis, looking along the layers of the crystal
</gallery>
 
== Појава ==
[[File:2005talc.png|thumb|left|250п|Talc output in 2005]]
Talc is a common metamorphic mineral in metamorphic belts that contain [[ultramafic rock]]s, such as [[soapstone]] (a high-talc rock), and within whiteschist and [[blueschist]] metamorphic [[terrane]]s. 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 [[Orogeny|orogens]] such as the [[Himalayas]], which stretch along [[Pakistan]], [[India]], [[Nepal]], and [[Bhutan]].
 
[[Talc carbonate]] ultramafics are typical of many areas of the [[Archean|Archaean]] [[craton]]s, 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).<ref>{{cite web|title=China, Brazil, the U.S. and India Remain the Major Consumers on the Global Talc Market |url=https://www.indexbox.io/blog/china-brazil-the-u-s-and-india-remain-the-major-consumers-on-the-global-talc-market/ |website=IndexBox |date=18 July 2018 |first=Anna |last=Sergeeva}}</ref>
 
== Конфликтни минерал ==
Extraction in disputed areas of [[Nangarhar province]], Afghanistan, has led the international monitoring group [[Global Witness]] to declare talc a [[conflict resource]], as the profits are used to fund armed confrontation between the [[Taliban]] and [[Islamic State of Iraq and the Levant|Islamic State]].<ref>{{cite web|title=Talc: the everyday mineral funding Afghan insurgents|url=https://www.globalwitness.org/en-gb/campaigns/afghanistan/talc-everyday-mineral-funding-afghan-insurgents/|website=Global Witness|access-date=24 May 2018|archive-date=24 May 2018|archive-url=https://web.archive.org/web/20180524222404/https://www.globalwitness.org/en-gb/campaigns/afghanistan/talc-everyday-mineral-funding-afghan-insurgents/|url-status=dead}}</ref>
 
== Употребе ==
[[File:Talcum Powder.JPEG|thumb|250п|Talcum powder]]
[[File:Talc.GIF|thumb|250п|The structure of talc is composed of Si<sub>2</sub>O<sub>5</sub> sheets with magnesium sandwiched between sheets in octahedral sites.]]
Talc is used in many industries, including paper making, [[plastic]], paint and coatings (e.g. for metal casting molds), rubber, food, electric cable, pharmaceuticals, cosmetics, and ceramics. A coarse grayish-green high-talc rock is [[soapstone]] or [[Soapstone|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 [[Cosmetics|cosmetic]] ('''talcum powder'''), as a [[lubricant]], and as a filler in paper manufacture. It is used to coat the insides of [[Tire#Associated components|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 [[Irritant diaper dermatitis|diaper rash]] (nappy rash). The [[American Academy of Pediatrics]] recommends that parents avoid using baby powder because it poses a risk of respiratory problems, including breathing trouble and serious lung damage if inhaled. 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.<ref>[http://www.babycenter.com/404_is-it-safe-to-use-baby-powder-on-my-baby_1519559.bc "Is it safe to use baby powder on my baby?"]. Babycenter.com (2017-05-01). Retrieved on 2017-05-06.</ref>
 
Soapstone (massive talc) is often used as a marker for [[welding]] or [[metalworking]].<ref>{{cite web |title=Why Do Welders Use Soapstone? |url=https://weldersmanual.com/why-do-welders-use-soapstone/ |website=Welders Manual |access-date=7 March 2022}}</ref><ref>{{cite web |last1=Young |first1=Pierre |title=What Is Soapstone Used for in Welding? |url=https://weldingheadquarters.com/what-is-soapstone-used-for-in-welding/ |website=Welding Headquarters |access-date=7 March 2022}}</ref>
 
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 [[E number|additive number]] is '''E553b'''. <br>
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.<ref>{{cite journal|title=Talc as friction reducing additive to lubricating oil|doi=10.1016/j.apsusc.2013.03.102|journal=Applied Surface Science|volume =276|year= 2013|pages =383–389|author1=Rudenko, Pavlo |author2=Bandyopadhyay, Amit |bibcode=2013ApSS..276..383R}}</ref>
Талк такође може да настане у реакцији доломита и силицијумдиоксида:
 
{| class="wikitable"
''[[Доломит]] + [[Силицијум диоксид]] + вода → Талк+ [[Калцит]] + Угљен-диоксид''
|-
:<math>3CaMg(CO_3)_2 + 4SiO_2 + H_2O \rarr Mg_3Si_4O_{10}(OH)_2 + 3CaCO_3 + 3CO_2</math>
! Type !! Talc content min. wt% !! Loss on ignition at 1000&nbsp;°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&nbsp;°C for talc compared to 1500&nbsp;°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 CO<sub>2</sub> per tonne used. This contrasts with a positive carbon footprint of 0.4 tonne per tonne of conventional cement.<ref name="guardian.co.uk">Jha, Alok (31 December 2008) [https://www.theguardian.com/environment/2008/dec/31/cement-carbon-emissions Revealed: The cement that eats carbon dioxide], ''The Guardian''</ref>
''[[Хлорит]] + [[Кварц]] → [[Кијанит]] + Талк + -{H}-<sub>2</sub>O''
 
== Сигурност ==
|url=http://www.meb.uni-bonn.de/cgi-bin/mycite?ExtRef=MEDL/92293722
|title=Perineal exposure to talc and ovarian cancer risk.
|author=Harlow, Cramer, Bell,
|year=1992
|journal=