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icosahedrite
Icosahedrite is the first known naturally occurring quasicrystal phase. It has the composition Al63Cu24Fe13 and is a mineral approved by the International Mineralogical Association in 2010.〔Commission on New Minerals and Mineral Names, (Approved as new mineral )〕 Its discovery followed a 10-year-long systematic search by scientists to find the first natural quasicrystal.
It occurs as tiny 0.1 mm grains in a small terrestrial rock sample labelled "khatyrkite, Khatyrka ultramafic zone, Koryak-Kamchatka area, Koryak Mountains, Russia", collected from an outcrop of weathered serpentinite (catalog number 46407/G, housed in The Museum of Natural History, University of Florence, Italy). The rock sample also contains spinel, diopside, forsterite, nepheline, sodalite, corundum, stishovite, khatyrkite, cupalite and an unnamed AlCuFe alloy. Intriguingly, evidence suggests icosahedrite is extraterrestrial in origin, possibly delivered to the Earth by a CV3 carbonaceous chondrite asteroid that dates back 4.5 Gya.〔 A geological expedition has identified the exact place of the original discovery and found more specimens.〔(Nadia Drake, ''Prospecting for Quasicrystals'', Science News, Print edition: Nov. 3, 2012; Vol.182 #9 (p. 24)/ Web edition: October 19, 2012 )
〕〔A second natural quasicrystal with a different (decagonal) structure has been identified in the samples, Bindi L., and al, ''Natural quasicrystal with decagonal symmetry'', (Nature - Scientific Reports ) 5, Article number: 9111 doi:10.1038/srep09111, 〕
The Al-Cu-Fe quasicrystal phase was originally created in the laboratory by Japanese experimental metallurgists in the late 1980s.
==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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