igneous

Olivine in Basalt (Peridot)

Magnesium Iron Silicate (Mg,Fe)2SiO4 (Mineral) / Scoriaceous Basalt (Host Rock)

Mineral Hardness: 6.5-7 (Mohs); Color: Olive-green, yellow-green; Luster: Vitreous to oily; Crystal structure: Orthorhombic; Specific gravity: 3.27–4.37; Host rock: Vesicular, dark grey/black, dull luster.

Hardness: 6
Color: Olive-green, yellow-green
Luster: Vitreous to oily

Identified February 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed in the Earth's upper mantle and brought to the surface by volcanic eruptions. The olivine crystals (phenocrysts) crystallize from mafic magma at extremely high temperatures as it cools. Most specimens are from the Neogene or Quaternary periods.

Uses & applications

Gem-quality olivine (Peridot) is used in jewelry; industrial olivine is used as a refractory material (furnace liners), a casting sand, and for CO2 sequestration research.

Geological facts

Olivine is the primary component of the Earth's upper mantle. It has also been discovered in meteorites (Pallasites) and on the surface of Mars and the Moon.

Field identification & locations

Identify by looking for glassy green granules embedded in a dark, porous volcanic matrix. Commonly found in basaltic lava fields such as those in Arizona (Peridot Mesa), Hawaii, and Iceland. Use a hand lens to check for a distinct 'sugary' grain texture and lack of cleavage.

Other igneous specimens

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral