igneous
Peridotite with olivine
Olivine-rich ultramafic rock; mainly forsterite–fayalite solid solution, (Mg,Fe)₂SiO₄
AI-generated identification · may be incorrectCoarse, granular, yellow-green olivine crystals in a dark ultramafic matrix; vitreous to greasy luster, no obvious cleavage, Mohs hardness 6.5–7, specific gravity about 3.2–4.3. Dark grains may be pyroxene or chromite.
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Physical properties
Coarse, granular, yellow-green olivine crystals in a dark ultramafic matrix; vitreous to greasy luster, no obvious cleavage, Mohs hardness 6.5–7, specific gravity about 3.2–4.3. Dark grains may be pyroxene or chromite.
Formation & geological history
A coarse intrusive mantle rock crystallized from magnesium- and iron-rich magma, commonly representing Earth’s upper mantle; typically Mesozoic to Precambrian in exposed terranes, though mantle material is far older. Weathering can produce serpentine.
Uses & applications
Used mainly as a teaching and collector specimen; olivine-rich material may be used as refractory aggregate, foundry sand, carbon-capture feedstock, or gemstone source when transparent (peridot).
Geological facts
The vivid green color is characteristic of abundant olivine, while black metallic grains may indicate chromite. Many peridotites originate as xenoliths brought rapidly to the surface by basaltic or kimberlitic magma.
Field identification & locations
Identify by its unusually high density, green granular crystals, lack of quartz, and possible magnetic or metallic chromite grains; common in ophiolites, mantle xenoliths, and volcanic fields in Hawaii, Arizona, Oman, and New Zealand.
