igneous

Basalt with Peridotite Inclusion

Mafic Volcanic Rock (Extrusive Igneous) with Ultramafic Xenolith

Hardness: 6-7 (Mohs). Color: Dark grey to black matrix with yellowish-green crystalline pockets. Luster: Dull to vitreous. Structure: Aphanitic (fine-grained) matrix with granular inclusions. Specific Gravity: 2.8 - 3.4.

Hardness: 6-7 (Mohs)
Luster: Dull to vitreous

Identified March 25, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava. The green inclusion (xenolith) is a piece of the Earth's mantle caught in the magma as it rose to the surface during a volcanic eruption.

Uses & applications

Basalt is used extensively in construction for aggregate, road base, and concrete. The peridotite (olivine) within it is used as a gemstone (peridot) when high quality, and industrially for refractory materials.

Geological facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The green inclusions (xenoliths) provide geologists with rare direct samples of the Earth's upper mantle from miles deep.

Field identification & locations

Identify in the field by its heavy weight and dark, fine-grained appearance. Look for 'glassy' green crystals embedded in a dark stone. Common in volcanic regions like Hawaii, Iceland, and the Canary Islands.

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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)

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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