- Stishovite
Infobox mineral
name = Stishovite
category = Mineral
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formula =Silica (silicon dioxide, SiO2)
molweight =
color = Clear (if no impurities); also see Varieties
habit =
system =
twinning =
cleavage =
fracture =
mohs = 9.4
luster =
refractive = nω = 1.81
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birefringence =
pleochroism =
streak =
gravity = 4.28 when pure
density =
melt = 1650 (±75) °C
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diagnostic =
solubility = 11.0 +/- 1.1 PPM @ 25 C
diaphaneity = Transparent to translucent
other =Stishovite (after S.M. Stishov, 20th-century Russian mineralogist) is an extremely hard, dense
tetragonal form (polymorph) ofsilicon dioxide . It was traditionally considered the hardest known oxide; however,boron suboxide was recently discovered to be much harder. At normal temperature and pressure, stishovite is metastable; it will eventually decay toquartz ; however, this phase change is slow enough that it has never been observed. Stishovite was first discovered in nature and named byEdward C. T. Chao .ynthesis
The only known occurrences of stishovite in nature formed at the very high shock pressures (>100 kbar = 10 GPa) and temperatures (> 1200°C) present during hypervelocity
meteorite impact intoquartz -bearing rock. Stishovite may also be synthesized by duplicating these conditions in the laboratory, either isostatically or through shock (seeshocked quartz ).ee also
*
Coesite , a related mineralReferences
[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TX4-41YG719-D&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5fe822b289eeed2f2e0e1bff9871860b High-pressure silica polymorphs as hardest known oxides]
External links
* [http://mineral.galleries.com/minerals/oxides/stishovi/stishovi.htm Properties of stishovite]
* [http://www.umich.edu/~gs265/meteor.htm Stishovite's origin in meteor impacts]
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