Stishovite

stishovite

coesite

keatite

seifertite

Images

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.
Silica minerals stability diagram
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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