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Olivine is a mineral formed from silica tetrahedra with magnesium (Mg+2) ions, or some other metal ion like manganese, iron, or calcium, in octahedral positions.

Olivine is one of the most important of the minerals making up the Earth. Olivines are a major constituent of the ultrabasic rocks (peroditites) in the upper part of the Earth's Mantle. They are to Gabbro and Basalt what Feldspars are to Granite and Rhyolite.

The olivine minerals include:

Forsterite (Mg2SiO4) (see Peridot)
Tephroite (Mn2SiO4)
Fayalite (Fe2SiO4)
Monticellite (CaMgSiO4)

Ol"i*vine (?), n. [Cf. F. olivine.] Min.

A common name of the yellowish green mineral chrysolite, esp. the variety found in eruptive rocks.


© Webster 1913.

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