What does dunite mean?
Dunite is an intrusive igneous rock that consists almost entirely of the mineral olivine — by geological convention, at least ninety percent. It belongs to the broader family of peridotites but represents their most olivine-rich end member, often appearing as pale green to yellowish-green, coarse-grained rock. Dunite commonly forms in the lower portions of ophiolite sequences, where it may represent depleted mantle rock from which basaltic melt has been extracted, and it also occurs as layers or lenses within large layered intrusions. Because it is so rich in olivine, dunite frequently hosts valuable ore deposits, particularly chromite, and has been studied as a potential reservoir for carbon sequestration owing to olivine's capacity to react with carbon dioxide. The rock takes its name from Dun Mountain near Nelson, New Zealand, where it was first described. Dunite remains chiefly a term of geology and petrology, valued for what it reveals about processes deep within the Earth's mantle.
nounA coarse-grained, ultramafic igneous rock composed almost entirely of the mineral olivine.
- An igneous rock consisting of at least 90% olivine, typically found in the lower parts of ophiolite complexes and layered intrusions.
"The peridotite body contained lenses of almost pure dunite."
"The mantle xenolith was composed of coarse-grained dunite flecked with chrome spinel."
"Miners once sought chromite seams within the dunite of the Great Dyke."
Usually treated as a mass noun when referring to the rock type; the plural appears mainly in geological literature referring to distinct occurrences or varieties of the rock.
"Several distinct dunites occur across the ophiolite belt."
Named after Dun Mountain in New Zealand — a mountain so full of green olivine that it's practically made of gemstone material.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of dunite
The word dunite derives from Dun Mountain, a peak near Nelson, New Zealand whose distinctive olive-green ultramafic rock caught geologists' attention in the mid-nineteenth century. The mountain itself takes its name from the dull brownish-green colour known as 'dun', which the weathered rock surface displays. The German-born geologist Ferdinand von Hochstetter described the rock during his 1859 survey of New Zealand, coining the term soon afterwards. The root connects it etymologically to colour words like dun and, through shared Indo-European ancestry, to terms such as dusk.
How dunite is actually used
Strictly a technical term used in geology and petrology; rarely encountered outside scientific literature. The name requires at least 90% olivine content by convention.
Easily confused with dunite
Peridotite is the broader family of olivine-rich rocks, while dunite is its most extreme member, containing over 90% olivine.