igneous

Basalt with Calcite Veining

Aphanitic Mafic Igneous Rock (primarily Plagioclase and Pyroxene)

Hardness: 6 (Mohs), Color: Dark grey to black with white veins, Luster: Dull/Earthy (matrix) to Vitreous (veining), Structure: Fine-grained aphanitic, Cleavage: None/Irregular

Identified May 26, 2026More igneous →

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Physical properties

Hardness: 6 (Mohs), Color: Dark grey to black with white veins, Luster: Dull/Earthy (matrix) to Vitreous (veining), Structure: Fine-grained aphanitic, Cleavage: None/Irregular

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the surface of a planet or moon. The white veins represent secondary mineralization where fluids deposited minerals like calcite or quartz in fractures long after the rock solidified.

Uses & applications

Commonly used as aggregate in construction, road base, and concrete. Small specimens with interesting veining are kept as educational or decorative garden stones.

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 found in abundance on the Moon and Mars.

Field identification & locations

Identify in the field by its dark color, heavy weight (high density), and fine grain. The presence of white veins that react with acid usually indicates calcite. Found globally in volcanic regions.

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

Dalmatian Jasper

Aplite with Arfvedsonite inclusions

igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral