igneous
Peridotite (Olivine)
Peridotite (comprising (Mg,Fe)2SiO4)
Hardness: 6.5-7 (Mohs); Color: Olive green to yellowish-green; Luster: Vitreous to granular; Crystal structure: Orthorhombic; Specific Gravity: 3.2-4.4; Cleavage: Poor
- Hardness
- 6
- Color
- Olive green to yellowish-green
- Luster
- Vitreous to granular
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Olive green to yellowish-green; Luster: Vitreous to granular; Crystal structure: Orthorhombic; Specific Gravity: 3.2-4.4; Cleavage: Poor
Formation & geological history
Formed deep within the Earth's mantle through the cooling of ultramafic magma. It is brought to the surface via volcanic activity (xenoliths) or tectonic uplifting. Common in Ophiolites.
Uses & applications
A major source of the gemstone peridot; also used as a source for magnesium and as a decorative stone in specific architectural contexts.
Geological facts
Peridotite is the dominant rock of the upper part of Earth's mantle. When it contains high-quality olivine, it produces the birthstone for August (Peridot). It is also known for its ability to sequester carbon dioxide from the atmosphere.
Field identification & locations
Identify by its distinctive olive-green granular texture and lack of quartz. Commonly found in basaltic lava flows or in alpine-type mountainous regions where mantle rock has been thrust onto the crust.
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