Lherzolite
Ultramafic peridotite (olivine + orthopyroxene + clinopyroxene)
The most common type of mantle peridotite, made of olivine with both orthopyroxene and clinopyroxene, representing fertile upper-mantle rock.
- Mohs hardness
- 6-7
- Color
- Green to yellowish-green, weathering brown
- Type
- igneous
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Overview
Lherzolite is a type of peridotite, an ultramafic rock dominated by olivine but containing significant amounts of both orthopyroxene and clinopyroxene. It is the classic representative of fertile upper-mantle material, meaning mantle that has not yet had large amounts of melt extracted from it.
Named after Lherz in the French Pyrenees, lherzolite carries an aluminous mineral, spinel or garnet, depending on the pressure at which it equilibrated. Garnet lherzolite forms deeper than spinel lherzolite.
Lherzolite is rarely seen at the surface, appearing mainly as xenoliths brought up by volcanoes or in tectonically uplifted mantle slices.
Formation & geology
Lherzolite makes up large portions of the Earth's upper mantle. It reaches the surface in two main ways: as xenoliths (mantle fragments) carried up rapidly by basaltic and kimberlitic magmas, and as massifs of mantle rock tectonically emplaced into the crust, such as in ophiolites and orogenic belts.
The aluminous phase records depth: plagioclase lherzolite forms at shallow levels, spinel lherzolite at intermediate depths, and garnet lherzolite deeper still. When partial melt is extracted from lherzolite, it leaves behind more refractory residues such as harzburgite and dunite.
How to identify it
Lherzolite is a dense, coarse-grained rock that is green to yellowish-green when fresh, often weathering to a brown rind. It shows granular olivine plus two pyroxenes, and either greenish spinel or red garnet as the diagnostic aluminous mineral.
Hardness is about 6-7 (olivine and pyroxene). Distinguish lherzolite from harzburgite and dunite by the presence of clinopyroxene (often greenish) in addition to orthopyroxene, and from pyroxenite by its dominant olivine. Fresh green olivine and red garnet grains are strong clues.
Uses & significance
Lherzolite has little direct economic use, though some peridotite bodies are sources of chromite, nickel, and platinum-group metals, and serpentinized peridotite can host talc and magnesite.
Its greatest value is scientific: lherzolite xenoliths and massifs provide direct samples of the Earth's upper mantle, helping geoscientists understand mantle composition, melting, and plate tectonics. It has no gemstone or metaphysical tradition, though it can carry gem-quality peridot (olivine).
Frequently asked questions
What is lherzolite made of?
Mostly olivine, plus both orthopyroxene and clinopyroxene, with an aluminous mineral (plagioclase, spinel, or garnet depending on depth).
Why is lherzolite important?
It is the main rock of the fertile upper mantle and provides scientists with direct samples of mantle composition.
How is lherzolite different from harzburgite?
Lherzolite contains clinopyroxene as well as orthopyroxene, while harzburgite is depleted in clinopyroxene, being a melt-extracted residue.
Where does lherzolite come from?
From the upper mantle, reaching the surface as volcanic xenoliths or as tectonically uplifted mantle massifs and ophiolites.
Lherzolite guides
In-depth guides for identifying, valuing, and understanding Lherzolite.
