igneous

Basalt

Mafic Igneous Rock

Hardness: 6-7 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-metallic. Crystal structure: Aphanitic (fine-grained), often contains micro-phenocrysts. Specific gravity: 2.8-3.0.

Hardness: 6-7 on Mohs scale
Color: Dark gray to black
Luster: Dull to sub-metallic

Identified March 18, 2026More igneous →

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Physical properties

Hardness: 6-7 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-metallic. Crystal structure: Aphanitic (fine-grained), often contains micro-phenocrysts. Specific gravity: 2.8-3.0.

Formation & geological history

Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron at or very near the Earth's surface. Common in oceanic crust and continental flood basalt provinces across all geological ages.

Uses & applications

Extensively used in construction as aggregate for roads, railway ballast, and in concrete. Often utilized as dimensional stone for paving and in high-strength industrial flooring.

Geological facts

Basalt is the most common rock type in the Earth's crust and even makes up the 'maria' (dark plains) on the Moon. It is also found in significant quantities on Mars and Venus.

Field identification & locations

Identify in the field by its high density, dark color, and fine texture with no visible individual crystals. It is found globally in volcanic regions like Hawaii, Iceland, and the Pacific Northwest.

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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