igneous

Basalt

Basalt (primarily composed of Plagioclase feldspar and Pyroxene)

Hardness: 6 on Mohs scale. Color: dark grey to black. Luster: dull to earthy. Crystal structure: fine-grained (aphanitic), often containing microscopic crystals. Specific gravity: 2.8–3.0.

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

Identified March 18, 2026More igneous →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6 on Mohs scale. Color: dark grey to black. Luster: dull to earthy. Crystal structure: fine-grained (aphanitic), often containing microscopic crystals. 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. It can be found in oceanic crust and volcanic regions worldwide.

Uses & applications

Extensively used in construction for aggregate in road base, concrete, and railroad ballast. Also used as dimension stone for statues and architecture, and occasionally in jewelry as 'lava rock' beads.

Geological facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floors. It is also common on the Moon and Mars—the dark 'seas' on the Moon (Maria) are actually giant basaltic plains.

Field identification & locations

Identify in the field by its dark color, heavy weight (high density), and fine-grained texture with no visible large crystals. It often breaks with a conchoidal fracture. Commonly found in volcanic fields or near coastal areas with ancient lava flows.

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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral