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Formula: SiO2 simple oxide, rutile group
Stishovite is an ultra-high pressure paramorph of
quartz; other paramorphs
include coesite, cristobalite,
keatite, mogánite,
seifertite and tridymite.
Specific gravity: 4.35 measured for synthetic material, 4.29
Hardness: 7¾ to 8
Colour: Colourless
Streak: White
Solubility: Insoluble in common acids and only very slowly soluble in HF
Environments:
Sedimentary environments
Meteorites
Stishovite formed from quartz through high transient shock pressure
and high temperature, in the impact craters of large
meteorites, where it is found as microscopic grains. Also
in ultra-high pressure rocks; it is an important component of subducted oceanic
basalts
(Mindat).
Localities
At the type locality, Meteor Crater, Meteor Crater area, Coconino County, Arizona, USA, stishovite occurs in
a meteor impact crater in
sandstone, associated with
coesite and quartz
(Mindat).
Alteration
Stishovite is a very high pressure paramorph of
quartz. With increasing pressure,
coesite alters to stishovite at about 90 kbar, and at about 2,770oC and
110 kbar pressure, coesite, stishovite and the silica melt
are in equilibrium
(QP).
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