igneous
Peridotite
Peridotite (composed largely of Olivine and Pyroxene)
Hardness: 6.5–7; Color: Dark green to greenish-grey or black; Luster: Dull to vitreous; Crystal structure: Orthorhombic; Specific Gravity: 3.2–3.4. It has a coarse-grained, phaneritic texture.
- Hardness
- 6
- Color
- Dark green to greenish-grey or black
- Luster
- Dull to vitreous
Identified More igneous →
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Physical properties
Hardness: 6.5–7; Color: Dark green to greenish-grey or black; Luster: Dull to vitreous; Crystal structure: Orthorhombic; Specific Gravity: 3.2–3.4. It has a coarse-grained, phaneritic texture.
Formation & geological history
Formed in the Earth's mantle through the slow cooling of ultramafic magma at high pressures and temperatures. It is often brought to the surface via tectonic uplift or volcanic pipes (xenoliths).
Uses & applications
Used as a source of magnesium, as a decorative stone, and as the parent rock for the gemstone peridot (olivine). It is also studied intensely for carbon sequestration research.
Geological facts
Peridotite is the dominant rock type of the Earth's upper mantle. When it reacts with water at low temperatures, it can transform into serpentinite.
Field identification & locations
Identified by its dark green color and heavy weight relative to its size. Look for it in ophiolites (fragments of oceanic crust on land) or as green nodules inside basaltic lava flows.
