igneous
Peridotite (Dunite)
Peridotite (mostly Olivine: (Mg,Fe)2SiO4)
Hardness: 6.5–7; Color: Olive-green, yellowish-green to brownish; Luster: Vitreous to greasy; Crystal Structure: Orthorhombic; Specific Gravity: 3.2–4.5
- Hardness
- 6
- Color
- Olive-green, yellowish-green to brownish
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 6.5–7; Color: Olive-green, yellowish-green to brownish; Luster: Vitreous to greasy; Crystal Structure: Orthorhombic; Specific Gravity: 3.2–4.5
Formation & geological history
Formed in the Earth's upper mantle through fractional crystallization of ultramafic magma. This specimen is likely an oceanic or mantle-derived ultramafic rock brought to the surface via plate tectonics or volcanic eruptions.
Uses & applications
Used as an ore for magnesium, as an abrasive, and high-quality olivine crystals (Peridot) are used in jewelry. In industry, it is used as a flux in steelmaking and for carbon sequestration research.
Geological facts
Peridotite is the primary rock type of the Earth's upper mantle. It is also found in some stony-iron meteorites (pallasites), making it an extraterrestrial mineral as well as a terrestrial one.
Field identification & locations
Identify in the field by its distinct 'olive' green color, granular (sugary) texture, and lack of quartz. Commonly found in ophiolitic complexes, volcanic 'bombs' (xenoliths) in basalt, or layered intrusions.
