Stishovite - Place of discovery: Nördlinger Ries, Germany — Photo: Raimond Spekking · CC BY-SA 4.0
Stishovite
The ultra-dense, ultra-hard silica polymorph formed by meteorite impact — a marker of shocked quartz.
Intro adapted from Wikipedia (CC BY-SA).
Stishovite is an IMA-recognized mineral species in the silicate class, with the chemical formula SiO₂.
It crystallizes in the tetragonal crystal system (space group P4_2/mnm). It is a member of the Rutile structural group.
Key properties: Mohs hardness 9–10; specific gravity 4.35; typically colorless or white or gray; white streak; vitreous luster; refractive index 1.818; optically uniaxial.
IMA symbol Sti, IMA status: approved, named in 1962.
At sites of meteorite impact, formed by shock metamorphism of quartz at temperatures ¸ 1200 ± C and pressures »100 kbar; then metastable, alters to glass or cristobalite at ¸ 300 ± C.
It is found associated with Coesite, quartz, silica glass.
In honor of the Russian crystallographer Sergei Mikhailovich Stishov, who, with S.V. Popova, first synthesized the compound.
Collections: Rare & Remarkable.