STISHOVITE

    Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Tetragonal
    Chemistry : SiO2
    Rarity : Very rare


Stishovite is an extremely rare form of silica that forms under very high pressures (over 80 kbars). It is a mineral specific to meteorite impact sites. This particular genesis leads to some disturbances: a crystal structure similar to that of rutile, and a very high density (4.3) for a form of silica resulting (unique case among silicates) from the position of silicon atoms in octahedral and not tetrahedral sites. It was named in honor of the crystallographer Sergei Mikhailovich Stishov of the Institute of Crystallography and the Academy of Sciences in Moscow. Stishovite never forms visible crystals.

Main photo : Stishovite from Meteor Crater, Arizona, USA © Giovanni Scapin

Stishovite in the World

Stishovite is found in tiny grains at meteorite impact sites such as Meteor Crater (Arizona), Lonar (India) or Popigar (Russia) where the colossal pressure conditions necessary for its genesis prevailed for a few milliseconds.

Stishovite in France

Stishovite is not present in the French underground.

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.



Hardness : 7.5 to 8
Density : 4.35
Fracture : Undetermined
Streak : White


TP : Transparent
RI : 1.799 to 1.845
Birefringence : 0.027
Optical character : Uniaxial +
Pleochroism : None
Fluorescence : None


Solubility : Hydrofluoric acid

Magnetism : NoneRadioactivity : None