Eclogite
Image: James St. John (CC BY 2.0)
Mineral NameEclogite
Chemical FormulaVariable, composed primarily of omphacite ((Ca,Na)(Mg,Fe,Al)Si2O6) and garnet ((Mg,Fe)3Al2(SiO4)3)
Mohs Hardness5
Streak ColorWhite to uncolored (not typically determined for a rock)
CleavageVariable, good in omphacite, absent in garnet
FractureConchoidal to uneven
Specific Gravity3.4
Colorsgreen, red, white, gray, blue, black
TransparencyOpaque (individual minerals can be translucent)
Type LocalityAlmenningen, Vestland, Norway
Mineral GroupMetamorphic rock
Usesscientific study, geological interest
Associated Mineralsgarnet (pyrope/almandine), omphacite pyroxene, quartz, kyanite, mica, rutile, amphibole
Rarityuncommon
Description
This is an attractive, uncommon, crystalline-textured, very high-grade metamorphic rock, characterized by reddish garnet and green omphacite pyroxene.
Geological Context
Eclogites are very high-grade metamorphic rocks that form in the Earth's mantle under extreme pressure and temperature conditions, typically brought to the surface in few places through tectonic processes.
