igneous

Olivine (Peridotite)

(Mg, Fe)2SiO4 (Magnesium Iron Silicate)

Hardness: 6.5–7.0 on Mohs scale; Color: Olive-green, yellow-green, or brownish; Luster: Vitreous (glassy); Crystal Structure: Orthorhombic; Cleavage: Poor; Specific Gravity: 3.2–4.4.

Hardness: 6
Color: Olive-green, yellow-green, or brownish
Luster: Vitreous (glassy)

Identified January 21, 2026More igneous →

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Physical properties

Hardness: 6.5–7.0 on Mohs scale; Color: Olive-green, yellow-green, or brownish; Luster: Vitreous (glassy); Crystal Structure: Orthorhombic; Cleavage: Poor; Specific Gravity: 3.2–4.4.

Formation & geological history

Formed deep in the Earth's mantle and brought to the surface via volcanic activity. It is the primary component of the upper mantle and constitutes intrusive igneous rocks like peridotite and extrusive basalt.

Uses & applications

Industrial uses include blast furnace flux for steel making and sand blasting. High-quality transparent specimens (Peridot) are used in jewelry.

Geological facts

Olivine is one of the first minerals to crystallize from magma (Bowen's Reaction Series). It has also been discovered in meteorites (Pallasites) and on the surface of Mars and the Moon.

Field identification & locations

Identify by its distinctive olive-green color and granular texture. It is commonly found in basaltic lava flows and ultramafic rock complexes. Collectors should look for 'xenoliths' or green nodules within darker volcanic rocks.

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Blue Apatite

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)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral