igneous

Basalt

Mafic Igneous Rock

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

Hardness: 6 (Mohs scale)
Color: Dark grey to black
Luster: Dull/Submetallic when fresh

Identified May 9, 2026More igneous →

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Physical properties

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

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. Most common rock on Earth's crust.

Uses & applications

Extensively used in construction for road base, concrete aggregate, railroad ballast, and dimension stone for paving. Some varieties are used in mineral wool insulation.

Geological facts

Basalt is the primary rock of the ocean floor and covers most of the volcanic islands like Hawaii and Iceland. It is also found on the Moon and Mars.

Field identification & locations

Identify by its dark color, heavy weight (relative to size), and fine-grained texture. Found near volcanic sites and oceanic crust outcrops.

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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