Dunite

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dunite

[′dü‚nīt]
(petrology)
An ultrabasic rock consisting almost solely of a magnesium-rich olivine with some chromite and picotite; an important source of chromium.

Dunite

 

(named after Mount Dün, New Zealand), a magmatic rock that is ultrabasic and black, dark-green, or light-green in color; it consists of 85 to 100 percent olivine and contains chromite as an admixture, sometimes together with magnetite. Dunite is very rich in magnesium and contains little silica. It is rarely found in an unchanged state; it is usually more or less serpentinized and even totally transformed into serpentine. Dunite is linked by gradual transitions with several gabbros and pyroxenites. Dunites are widespread; they usually form sills, parallel lenses, and intersecting pipes; more seldom they form large intrusive bodies (for example, the dunite belts along the entire Urals and the Mugodzhary). It is thought that dunites are chunks of the upper mantle that were tectonically introduced into the young rocks of the upper part of the earth’s crust. Deposits of various minerals (including chromites, platinum, nickel, cobalt, talc, and chrysotile-asbestos) are associated with dunite. Dunite is used for the manufacture of fire-resistant materials.