igneous

Peridotite (Olivine/Peridot)

Peridotite: (Mg,Fe)2SiO4 (Olivine-rich ultramafic rock)

Hardness: 6.5–7; Color: Olive-green, yellowish-green; Luster: Vitreous to dull; Structure: Granular/Crystalline; Specific Gravity: 3.2–3.4; Cleavage: Poor/Conchoidal fracture.

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

Identified April 11, 2026More igneous →

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Physical properties

Hardness: 6.5–7; Color: Olive-green, yellowish-green; Luster: Vitreous to dull; Structure: Granular/Crystalline; Specific Gravity: 3.2–3.4; Cleavage: Poor/Conchoidal fracture.

Formation & geological history

Formed in the Earth's mantle through slow cooling of ultramafic magma. It is a major constituent of the upper mantle and is often brought to the surface by volcanic activity as xenoliths.

Uses & applications

Primary source of the gemstone peridot; also used as a decorative stone and for carbon sequestration research. Historically used as a source of magnesium and chromium.

Geological facts

Peridotite is the main rock type of the Earth's upper mantle. Gem-quality olivine within it is known as Peridot, which is the birthstone for August.

Field identification & locations

Identify by its distinctive olive-green color and granular texture. Commonly found in volcanic areas (Hawaii, Arizona) and ophiolite complexes. Look for small, glassy green crystals embedded in darker basaltic matrix.

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Fluorapatite (Ca5(PO4)3F)

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

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Magnetite

Magnetite (Fe3O4)

mineral