Mineral Information and Data:

Clinoenstatite
MgSiO3 [CNMNC approved formula]

Named in 1906 as the monoclinic polymorph of enstatite.

IMA status : Approved Species 1988 ()
CLASSIFICATION 
Dana
(8th edition) :
65.01.01.01  
  (65) Inosilicate Single-Width Unbranched Chains, W=1
  (65.01) with chains P=2
  (65.01.01) P2/c clinopyroxenes
  
Nickel-Strunz
(10th edition) :
09.DA.10
  (09) Silicates
  (09.D) Inosilicates* Structural terminology per Liebau (1985)
  (09.DA) with 2-periodic single chains, Si2O6; pyroxene family
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 9.6Å, b = 8.81Å, c = 5.17Å β = 108.28°
Crystal Habit: Crystals short prismatic or tabular; massive, lamellar
  
Color: Colorless, yellow-brown, greenish
Diaphaneity: Transparent to translucent
Luster: Vitreous
Hardness (Mohs): 5 to 6
Measured Density: 3.19 g/cm3
Cleavage: 1; {110} distinct
Tenacity: Brittle
Streak: White
  
Polymorphism and Series: Dimorphous with enstatite
Geologic Setting: As phenocrysts, likely inverted from "protoenstatite," in high-magnesium nonfeldspathic andesites. Exsolved in diopside in ultramafic rocks and in enstatite in high-grade metamorphic hornfelses. An essential constituent of chondrite and achondrite meteorites, likely formed by stress.
Mineral Association: Diopside, enstatite, chromite, "hypersthene," glass
  

 

Clinoenstatite
0,9 mm twinned crystal - probably clinohypersthene : median term between the two poles of the solid solution clinoenstatite-clinoferrosilite.
Origin : Burande brook alluvials, Singles, Tauves, Puy-de-Dôme,
Auvergne, France
Photo and collection François Périnet.

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