igneous

Basalt with Quartz/Calcite Inclusions

Mafic Volcanic Rock (Fe-Mg silicate rich)

Hardness: 5-6 Mohs for matrix, 7 for quartz; Color: Dark grey to black with white patches; Luster: Dull/earthy matrix, vitreous inclusions; Crystal structure: Aphanitic (fine-grained) matrix; Density: High (2.8–3.0 g/cm3).

Hardness: 5-6 Mohs for matrix, 7 for quartz
Color: Dark grey to black with white patches
Luster: Dull/earthy matrix, vitreous inclusions

Identified April 1, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The white inclusions likely represent secondary mineral growth (vesicle filling) or phenocrysts formed during later stages of cooling.

Uses & applications

Common basalt is used in construction as aggregate for roads, railroad ballast, and in the manufacturing of stone wool insulation. Decorative specimens are used in landscaping.

Geological facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also extremely common on the Moon and Mars.

Field identification & locations

Identify in the field by its dark color, heavy weight for its size, and fine-grained texture that lacks visible individual crystals in the dark matrix. Look for small holes (vesicles) or white mineral spots.

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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