igneous

Basalt

Basalt (Aphanitic Mafic Igneous Rock)

Hardness: 6 (Mohs scale); Color: dark grey to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic), sometimes vesicular; Specific gravity: 2.8–3.0

Hardness: 6 (Mohs scale)
Color: dark grey to black
Luster: dull to earthy

Identified May 30, 2026More igneous →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6 (Mohs scale); Color: dark grey to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic), sometimes vesicular; 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.

Uses & applications

Extensively used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Can also be used as a dimension stone for flooring or monuments.

Geological facts

Basalt is the most common rock type in the Earth's crust, covering most of the ocean floor. It is also found on the Moon, Mars, and Venus.

Field identification & locations

Look for a heavy, dark-colored, fine-grained rock. It often breaks into angular pieces. Widely found in volcanic regions such as the Pacific Northwest, Hawaii, and Iceland.

Other igneous specimens

See all

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