Kosmochlor

Kosmochlor is a rare chromium sodium clinopyroxene with the chemical formula NaCr3+Si2O6.

Kosmochlor
Kosmochlor jade, Jurassic, Burma 1.jpg
Chromite (metallic black), kosmochlor pyroxene (emerald green to dark green to black), chromian jadeite pyroxene (green), chromiferous arfvedsonite amphibole (green or gray), symplectite (green, a finely-crystalline mineral mix of mostly chromian jadeite)
General
CategoryInosilicate mineral
Formula
(repeating unit)
NaCr3+Si2O6
Strunz classification9.DA.25
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Unit cella = 9.57, b = 8.71
c = 5.26 Å; β = 107.49°; Z = 4
Identification
ColorEmerald-green
Crystal habitPrismatic crystals and fibrous aggregates
TwinningSimple, lamellar on {100} and {001}
CleavageGood on {110} parting on {001}
Mohs scale hardness6
LusterVitreous
StreakLight green
DiaphaneitySemitransparent
Specific gravity3.51-3.60
Optical propertiesBiaxial (-)
Refractive indexnα = 1.766 nγ = 1.781
Birefringenceδ = 0.015
PleochroismX = yellowish green; Y = blue-green, grass-green; Z = emerald-green
Dispersionr > v
References[1][2][3]

The name is from German kosmisch, for its occurrence in meteorites, and the Greek chlor, for green.[3] It was first reported in 1897 from the Toluca meteorite, Jiquipilco, Mexico.[1]

It occurs as a major constituent of some jadeitites and as an accessory mineral of some iron meteorites. Associated minerals include cliftonite (graphite), chromian diopside, troilite at Toluca; daubreelite, krinovite, roedderite, high albite, richterite, chromite (Canyon Diablo); and jadeite, chromite and chlorite (Burma).[2]

ReferencesEdit