Omphacit im Dünnschliff in linear-polarisiertem Licht — Photo: Ringwoodit · CC BY-SA 4.0
Omphacite
A deep-green clinopyroxene of high-pressure rocks — the defining mineral of eclogites.
Intro adapted from Wikipedia (CC BY-SA).
Omphacite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Ca,Na)(Mg,Fe,Al)Si₂O₆.
It crystallizes in the monoclinic crystal system (space group P2/n). It is a member of the Pyroxene structural group.
Key properties: Mohs hardness 5–6; specific gravity 3.16–3.43; typically green; white streak; Vitreous to silky luster; refractive index 1.692; optically biaxial.
IMA symbol Omp, IMA status: approved, named in 1815.
A major constituent of eclogite, commonly in kimberlite pipes; from some ophiolites and glaucophane-bearing blueschist facies rocks.
It is found associated with Garnet, quartz, kyanite, corundum (eclogite); \hornblende, " scapolite, epidote, glaucophane (blueschists).
Its name comes from the Greek for unripe grape, in allusion to its green color.
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