Igneous

Peridotite

Ultramafic intrusive rock (Peridotite)

Hardness: 6.5–7 (Mohs scale); Color: Olive-green, dark green to black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained), typically granular; Specific gravity: 3.2–3.4; Composition: Principally olivine and pyroxene.

Hardness: 6
Color: Olive-green, dark green to black
Luster: Vitreous to dull

Identified March 7, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow cooling of ultramafic magma deep within the Earth's mantle or at the base of the crust. It is a primary constituent of the Earth's upper mantle and can be uplifted during tectonic events or as xenoliths in volcanic eruptions.

Uses & applications

Primary source of magnesium and chromium ores (chromite). In construction, it is used as crushed stone for road bases. Large, gem-grade olivine crystals from peridotite are known as Peridot and used in jewelry.

Geological facts

Peridotite is thought to be the most abundant rock type in the Earth's upper mantle. It is often scientifically studied to understand the composition of the deep Earth and the process of mantle convection.

Field identification & locations

Identify in the field by its distinct dark olive-green color and coarse-grained, 'sugary' texture. Locations include ophiolite complexes (e.g., Oman, Cyprus) and mantle xenoliths in basalt flows. Collectors look for bright green olivine phenocrysts.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous