Eskolaite

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Eskolaite
Eskolaite.jpg
Eskolaite from Russia
General
Category Oxide mineral
Hematite group
Corundum structural group
Formula
(repeating unit)
Cr2O3
Strunz classification 04.CB.05
Crystal symmetry Trigonal hexagonal scalenohedral
H-M symbol: (32/m)
Space group: R3c
Unit cell a = 4.95 Å, c = 13.58 Å; Z=6
Identification
Color Black to dark green
Crystal habit Hexagonal prisms and plates
Crystal system Trigonal
Cleavage None
Tenacity Brittle
Mohs scale hardness 8
Luster Vitreous or metallic
Streak Pale green
Diaphaneity Opaque, translucent in thin edges
Specific gravity 5.18
Optical properties Uniaxial
Pleochroism Noted; emerald-green to olive-green
References [1][2][3]

Eskolaite is an uncommon chromium oxide mineral (chromium(III) oxide Cr2O3).

Discovery and occurrence[edit]

It was first described in 1958 for an occurrence in the Outokumpu ore deposit of eastern Finland.[2] It occurs in chromium bearing tremolite skarns, metamorphosed quartzites and chlorite bearing veins in Finland; in glacial boulder clays in Ireland and in stream pebbles in the Merume River of Guyana.[1] It has also been recognized as a rare component in chondrite meteorites.[1]

References[edit]