Examine individual changes

'{{Infobox mineral | name = Moissanite | category = [[Mineral]] species | image = Moissanite-USGS-20-1001d-14x-.jpg | imagesize = 260px | caption = | formula = SiC | molweight = | strunz = 1.DA.05 | system = 6H polytype, most common: [[Hexagonal crystal system|hexagonal]] | class = 6H polytype: dihexagonal pyramidal (6mm) <br/>[[H-M symbol]]: (6mm) | symmetry = 6H polytype: ''P6''₃mc | color = Colorless, green, yellow | habit = Generally found as inclusions in other minerals | twinning = | cleavage = (0001) indistinct | fracture = Conchoidal – fractures developed in brittle materials characterized by smoothly curving surfaces, ''e.g.'', quartz | mohs = 9.5 | luster = Adamantine to metallic | refractive = n_ω=2.654 n_ε=2.967, [[Birefringence]] 0.313 (6H form) | opticalprop = | birefringence = | fluorescence= orange-red | pleochroism = | streak = greenish gray | gravity = 3.218–3.22 | melt = 2730 °C (decomposes) | fusibility = | diagnostic = | solubility = none | diaphaneity = transparent | other = Not radioactive, non-magnetic | references = <ref>[http://www.webmineral.com/data/Moissanite.shtml Moissanite]. Webmineral</ref><ref>[http://www.mindat.org/min-2743.html Moissanite]. Mindat</ref><ref name=Handbook>Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W. and Nichols, Monte C. (eds.) [http://www.handbookofmineralogy.org/pdfs/moissanite.pdf "Moissanite"]. ''Handbook of Mineralogy''. Mineralogical Society of America</ref> }} '''Moissanite''' ({{IPAc-en|ˈ|m|ɔɪ|s|ən|aɪ|t}})<ref>{{OED|Moissanite}}</ref> is naturally occurring [[silicon carbide]] and its various crystalline [[Polymorphism (materials science)|polymorphs]]. It has the chemical formula SiC and is a rare mineral, discovered by the French chemist [[Henri Moissan]] in 1893. Silicon carbide is useful for commercial and industrial applications due to its hardness, optical properties and thermal conductivity. Efforts to synthesize silicon carbide in a laboratory began in the early 1900s.{{Citation needed|reason=Reliable source needed for the whole sentence|date=February 2018}} == Background == Mineral moissanite was discovered by Henri Moissan while examining rock samples from a meteor crater located in [[Canyon Diablo (canyon)|Canyon Diablo]], [[Arizona]], in 1893. At first, he mistakenly identified the crystals as diamonds, but in 1904 he identified the crystals as silicon carbide.<ref name = xu>{{cite journal|author = Xu J. |author2=Mao H. |last-author-amp=yes |date = 2000| title = Moissanite: A window for high-pressure experiments|journal = [[Science (journal)|Science]]|volume = 290| pages = 783–787|doi = 10.1126/science.290.5492.783|pmid=11052937|issue=5492|bibcode = 2000Sci...290..783X }}</ref><ref>{{cite journal|author = Moissan, Henri |title = Nouvelles recherches sur la météorité de Cañon Diablo|date = 1904|journal = [[Comptes rendus]]|volume = 139| pages = 773–786| url = http://gallica.bnf.fr/ark:/12148/bpt6k30930/f773.table}}</ref> Artificial silicon carbide had been synthesized in the lab by [[Edward_Goodrich_Acheson|Edward G. Acheson]] just two years before Moissan's discovery.<ref>{{cite web|last1=Smith|first1=Kady|title=History and Applications of Silicon Carbide|url=http://blog.moissaniteco.com/history-and-applications-of-silicon-carbide/|publisher=Moissanite & Co|accessdate=2 February 2016}}</ref> The mineral form of silicon carbide was named moissanite in honor of Moissan later on in his life. The discovery in the [[Canyon Diablo (meteorite)|Canyon Diablo meteorite]] and other places was challenged for a long time as [[Silicon carbide|carborundum]] contamination from man-made abrasive tools.<ref name = pierro>{{cite journal|author = Di Pierro S. |display-authors=4 |author2= Gnos E. |author3=Grobety B.H. |author4=Armbruster T. |author5=Bernasconi S.M. |author6=Ulmer P. |last-author-amp=yes |date = 2003|title = Rock-forming moissanite (natural α-silicon carbide)|journal = American Mineralogist|volume = 88|pages = 1817–1821|url = http://www.geoscienceworld.org/cgi/georef/2004018181|bibcode=2003AmMin..88.1817D|doi=10.2138/am-2003-11-1223}}</ref> == Geological occurrence == Until the 1950s no other source, apart from meteorites, had been encountered. Later moissanite was found as [[Inclusion (mineral)|inclusions]] in [[kimberlite]] from a diamond mine in [[Sakha Republic|Yakutia]] in 1959, and in the [[Green River Formation]] in [[Wyoming]] in 1958.<ref>{{cite journal|journal = American Mineralogist|volume =48|pages = 620–634|date = 1963|title = Natural α–Silicon Carbide|author = Bauer, J.|author2=Fiala, J. |author3=Hřichová, R. |url=http://www.minsocam.org/msa/collectors_corner/arc/moissanite.htm}}</ref> The existence of moissanite in nature was questioned even in 1986 by Charles Milton, an American geologist.<ref>{{cite journal|journal = American Mineralogist|volume =79|pages = 190–192|date = 1994|title = Memorial of Charles Milton April 25, 1896 – October 1990|url=http://www.minsocam.org/ammin/AM79/AM79_190.pdf|author = Belkin, H. E. |author2=Dwornik, E. J. }}</ref> Moissanite, in its natural form, is very rare. It has been discovered only in a small variety of places from upper [[Mantle (geology)|mantle]] rock to [[meteorite]]s. Discoveries have shown that moissanite occurs naturally as inclusions in diamonds, [[xenolith]]s, and [[ultramafic rock]]s such as [[kimberlite]] and [[lamproite]].<ref name = pierro/> They have also been identified in [[carbonaceous chondrite]] meteorites as [[presolar grains]].<ref name = sch>{{cite journal|author = Yokoyama, T. | author2=Rai, V. K. | author3=Alexander, C. M. O’D. | author4=Lewis, R. S. | author5=Carlson, R. W. | author6=Shirey, S. B. | author7=Thiemens, M. H. | author8=Walker, R. J. |title = Nucleosynthetic Os Isotopic Anomalies in Carbonaceous Chondrites|url=http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1151.pdf|journal = 38th Lunar and Planetary Science Conference |date=March 2007}}</ref> ==Meteorites== Analysis of silicon carbide grains found in the [[Murchison meteorite]] has revealed anomalous isotopic ratios of carbon and silicon, indicating an origin from outside the solar system.<ref>Kelly, Jim. [http://img.chem.ucl.ac.uk/www/kelly/history.htm The Astrophysical Nature of Silicon Carbide]. chem.ucl.ac.uk</ref> 99% of these silicon carbide grains originate around carbon-rich [[asymptotic giant branch]] stars. Silicon carbide is commonly found around these stars, as deduced from their infrared spectra.{{Citation needed|date=February 2016}} == Sources == All applications of silicon carbide today use [[Silicon carbide#Production|synthetic material]], as the natural material is very scarce. Silicon carbide was first synthesized by [[Jöns Jacob Berzelius]], who is best known for his discovery of [[silicon]].<ref name = saddow>{{cite book| author = Saddow S.E. |author2=Agarwal A. |last-author-amp=yes |date = 2004| title = Advances in Silicon Carbide Processing an Applications|publisher = Artech House Inc.|url = https://books.google.com/books?id=2jSPO_JtQwEC|isbn = 1-58053-740-5}}</ref> Years later, [[Edward Goodrich Acheson]] produced viable minerals that could substitute for diamond as an abrasive and cutting material. This was possible, as moissanite is one of the hardest substances known, with a hardness below that of [[diamond]] and comparable with those of cubic [[boron nitride]] and [[boron]]. Pure synthetic moissanite can be made from thermal decomposition of the preceramic polymer [[poly(methylsilyne)]], requiring no binding matrix, ''e.g.'', cobalt metal powder. == Physical properties == {{main article|Silicon carbide}} The crystalline structure is held together with strong [[covalent bonding]] similar to diamonds,<ref name = xu/> that allows moissanite to withstand high pressures up to 52.1 [[gigapascal]]s.<ref name = xu/><ref name = zhang>{{cite journal|author = Zhang J. |display-authors=4 |author2= Wang L. |author3=Weidner D.J. |author4=Uchida T. |author5=Xu J. |last-author-amp=yes |date = 2002| title = The strength of moissanite |journal = American Mineralogist|volume = 87| pages = 1005–1008 |url = http://www.minsocam.org/msa/AmMin/toc/Abstracts/2002_Abstracts/July02_Abstracts/Zhang_p1005_02.pdf|format=PDF|bibcode=2002AmMin..87.1005Z|doi=10.2138/am-2002-0725}}</ref> Colors vary widely and are graded from D to K range on the [[Diamond color|diamond color grading scale]].<ref name = Read>{{cite book| author = Read P.|date = 2005| title = Gemmology |publisher = Elsevier Butterworth-Heinemann| place = Massachusetts|url = https://books.google.com/books?id=t-OQO3Wk-JsC| isbn = 0-7506-6449-5}}</ref> == Applications == {{main article|Silicon carbide#Uses}} [[File:Moissanite_ring_natural_light.jpg|thumb|right|A moissanite engagement ring]] Moissanite was introduced to the jewelry market in 1998 after [[Charles & Colvard]], formerly known as C3 Inc., received patents to create and market lab-grown silicon carbide gemstones, becoming the first firm to do so. Charles & Colvard currently makes and distributes moissanite jewelry and loose gems under the trademarks Forever One, Forever Brilliant and Forever Classic.<ref>{{cite web|title=Moissanite Rights|url=http://www.professionaljeweler.com/archives/articles/1998/may98/0598press1.html|publisher=Professional Jeweler Magazine|accessdate=24 October 2012|date=May 1998}}</ref> Other manufacturers market silicon carbide gemstones under trademarked names such as Amora and Berzelian. Moissanite is regarded as a [[diamond alternative]], with some optical properties exceeding those of diamond. Its lower price and less exploitative mining practices necessary to obtain it make it a popular alternative to diamonds. Due in part to the similar thermal conductivity of moissanite and diamond, it is a popular target for scams; however, higher electrical conductivity and [[birefringence]] of moissanite may alert a buyer to fraud. In addition, [[thermochromism]] is exhibited in moissanite, such that heating it gradually will cause it to change color starting at around {{convert|65|C|abbr=on|-1}}. This color change can be diagnostic for distinguishing diamond from moissanite, although birefringence and electrical conductivity differential are more practical diagnostic differentiators.<ref>[http://www.gemsociety.org/article/diamond-look-alike-comparison-chart/ Diamond Look-Alike Comparison Chart]. International Gem Society</ref> On the [[Mohs scale of mineral hardness]] it is a 9.5, with a diamond being a 10.<ref name=Handbook/> In many developed countries, the use of moissanite in jewelry was controlled by the patents held by Charles & Colvard; these patents expired in August 2015 for the United States, and in 2016 in most other countries except Mexico, where it remained under patent until 2018.<ref>Hunter, Charles Eric and Verbiest, Dirk (1995-08-31) {{US Patent|5762896}} "Single crystal gems hardness, refractive index, polishing and crystallization "</ref><ref>Hunter, Charles Eric and Verbiest, Dirk (1995-08-31) {{US Patent|5723391}} "Silicon carbide gemstones"</ref><ref>{{cite web|title=Moissanite Gem Patent Restrictions by Country and Year of Expiration|url=http://betterthandiamond.com/pages/Moissanite-Gem-Patent-restrictions-by-country-and-year-of-expiration.html|work=BetterThanDiamond}}</ref> Because of its hardness, it can be used in high-pressure experiments, as a replacement for diamond (see [[diamond anvil cell]]).<ref name = xu/> Since large diamonds are usually too expensive to be used as anvils, synthetic moissanite is more often used in large-volume experiments. Synthetic moissanite is also interesting for [[electronics|electronic]] and thermal applications because its [[thermal conductivity]] is similar to that of diamonds.<ref name = zhang/> High power silicon carbide electronic devices are expected to find use in the design of protection circuits used for motors, [[actuator]]s, and energy storage or pulse power systems.<ref name=baliga>{{cite journal|last=Bhatnagar|first=M.|author2=Baliga, B.J.|title=Comparison of 6H-SiC, 3C-SiC, and Si for power devices|journal=IEEE Transactions on Electron Devices|date=1993|volume=40|issue=3|pages=645–655|doi=10.1109/16.199372 |bibcode = 1993ITED...40..645B }}</ref> It also exhibits [[thermoluminescence]],<ref>{{cite journal|last1=Godfrey-Smith|first1=D.I.|title=Applicability of moissanite, a monocrystalline form of silicon carbide,to retrospective and forensic dosimetry|journal=Radiation Measurements|date=Aug 1, 2006|volume=Volume 41|issue=7|url=https://www.deepdyve.com/lp/elsevier/applicability-of-moissanite-a-monocrystalline-form-of-silicon-carbide-Uaw0AcXWN0|accessdate=23 December 2017}}</ref> making it useful in radiation [[dosimetry]].<ref>{{cite journal|last1=Bruzzia|first1=M.|last2=Navab|first2=F.|last3=Piniac|first3=S.|last4=Russoc|first4=S.|title=High quality SiC applications in radiation dosimetry|journal=Applied Surface Science|date=12 December 2001|volume=Volume 184|issue=1-4|pages=Pages 425-430|doi=10.1016/S0169-4332(01)00528-1|url=http://www.sciencedirect.com/science/article/pii/S0169433201005281|accessdate=23 December 2017|bibcode=2001ApSS..184..425B}}</ref> ==See also== *[[Glossary of meteoritics]] *[[Engagement ring]] *[[Fair trade]] *[[Charles & Colvard]] *[[Diamond]] *[[Cubic zirconia]] ==References== {{Reflist|30em}} == Further reading == {{commons category|Moissanite}} * {{cite journal|last=Nassau|first=Kurt|date=1999|title=Moissanite: a new synthetic gemstone material|journal=Journal of Gemmology|volume=26|issue=7|pages= 425–438|url=http://www.moissaniteco.com/pdf/Synthetic-Moissanite-A-New-Man-Made-Jewel.pdf}} {{Meteorites}} [[Category:Meteorite minerals]] [[Category:Carbide minerals]] [[Category:Hexagonal minerals]] [[Category:Native element minerals]]'