igneous

Basalt

Basalt (Mafic Extrusive)

Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull/earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: None/clastic; Specific gravity: 2.8 - 3.0.

Hardness: 6 on Mohs scale
Color: Dark grey to black
Luster: Dull/earthy

Identified April 10, 2026More igneous →

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Physical properties

Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull/earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: None/clastic; Specific gravity: 2.8 - 3.0.

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava (mafic) exposed at or very near the surface of a terrestrial planet or a moon. Most basalt flows are from the Cenozoic era, though it can date back billions of years.

Uses & applications

Used primarily in construction for crushed stone, road base, concrete aggregate, and railroad ballast. High-quality dense basalt is also used for floor tiles and architectural veneers.

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 on the Moon, Mars, and Venus in large quantities.

Field identification & locations

Identify in the field by its dark color, heavy weight (density), and fine-grained texture lacking visible crystals. Commonly found in volcanic fields, ocean ridges, and flood basalt provinces like the Deccan Traps or Columbia River Plateau.

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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