igneous

Basalt (Drill Core)

Mafic Volcanic Rock (Basalt)

Hardness: 6 on Mohs scale; Color: Dark grey to black with green/black phenocrysts; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained) with visible porphyritic crystals; Specific gravity: 2.8-3.0.

Hardness: 6 on Mohs scale
Color: Dark grey to black with green/black phenocrysts
Luster: Dull/Matte

Identified April 6, 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. This specimen appears to be a section of a diamond-drill core used in mining exploration.

Uses & applications

Used primarily as crushed stone for aggregate in concrete and asphalt, road base, and railroad ballast. Drill cores specifically are used for geological mapping and ore deposit exploration.

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 extensively on the Moon and Mars.

Field identification & locations

Identify by its dark color, heavy weight (density), and fine-grained texture. For drill cores, look for circular striations on the outer surface from the diamond bit's rotation.

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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