Peridotite (Pyroxenite/Serpentinized Dunite)

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Dark green to brownish-black with possible olive-green hues; Luster: Greasy to vitreous; Crystal structure: Orthorhombic/Monoclinic; Cleavage: Poor/Imperfect; Specific gravity: 3.2-3.4

Formation & Geological History

Formed in the Earth's mantle or lower crust through slow cooling of magma. These rocks are usually brought to the surface via tectonic plate movement or volcanic eruptions (e.g., as xenoliths). Most are Pre-Cambrian to Mesozoic in age.

Uses & Applications

Primary source of chromium, nickel, and platinum; high-quality olivine varieties (peridot) are used in jewelry; historically used as a decorative stone or for crushed aggregate.

Geological Facts

Peridotite is the dominant rock of the upper part of Earth's mantle and is extremely rare as a surface rock. It can capture carbon dioxide from the atmosphere when it undergoes weathering, making it a subject of study for climate change mitigation.

Field Identification & Locations

Identify by its heavy weight (high density), dark green crystalline appearance, and common presence of brown weathering rinds (oxidation). Usually found in ophiolite complexes where mantle material has been thrust onto continental crust.

Identified on: 4/14/2026

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