igneous

Basalt (with possible quartz veinsing)

Basalt

Hardness: 6 (Mohs scale); Color: Dark grey to black with white secondary mineral veins; Luster: Dull/Sub-metallic; Crystal Structure: Aphanitic (fine-grained/microscopic); Cleavage: None; Specific Gravity: 2.8-3.0.

Hardness: 6 (Mohs scale)
Color: Dark grey to black with white secondary mineral veins
Luster: Dull/Sub-metallic

Identified March 22, 2026More igneous →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specimen appears to have undergone secondary mineralization where silica-rich fluids filled fractures to create the white veins.

Uses & applications

Commonly used as aggregate in construction (roads and concrete), railroad ballast, and ground-up for industrial abrasives. Polished basalt is also used for decorative flooring and landscaping.

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 other celestial bodies including the Moon, Mars, and Venus.

Field identification & locations

Identify by its heavy weight (high density), dark color, and lack of visible crystals. It is commonly found in volcanic regions, near ocean ridges, and as water-worn pebbles in riverbeds or beaches near volcanic outflows.

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