CLINOENSTATITE

    Class : Silicates
    Subclass : Inosilicates
    Crystal system : Monoclinic
    Chemistry : MgSiO3
    Rarity : Rare

Clinoenstatite belongs to the group of pyroxenes. It is a rare dimorph of enstatite which forms a continuous series with clinoferrosilite. Its name is related to its monoclinic crystal system and its chemical similarity to enstatite. It is found in short to tabular prismatic crystals of 2 mm at most, frequently twinned, and in lamellar masses in rare magnesian andesites, in ultrabasic diopside rocks and hornfels with a strong metamorphic gradient. On the other hand, it is an essential constituent of chondrites and achondrites. Clinoenstatite is usually brown to greenish gray.

Main photo : Clinoenstatite from the alluvial deposits of Dordogne, Puy-de-Dôme, France © François Périnet

Clinoenstatite in the World

Clinoenstatite is rare, its best crystals seem to be complex twinned millimeter phenocrysts from Cape Vogel (Papua New Guinea). Clinoenstatite is also known in the andesites of the Bonin archipelago (Japan), as well as in a few other localities.

Right photo : Clinoenstatite from Arsenatnaya, Tolbachik Volcanic Fields, Russia © Stephan Wolfsried

Clinoenstatite in France

Beautiful crystals have been discovered in the alluvial deposits of the Dordogne and Burande near Issoire (Puy-de-Dôme).

Twinning

Polysynthetic twins on {100} are known for this mineral species.

Fakes and treatments

No fake identified for this mineral species.


Hardness : 5 to 6
Density : 3.21
Fracture : Conchoidal
Streak : White

TP : Translucent to transparent
RI : 1.651 to 1.660
Birefringence : 0.009
Optical character : Biaxial +
Pleochroism : Visible
Fluorescence : None

Solubility : Insoluble


Magnetism : None
Radioactivity : None