Basalt

Physical Properties

Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Cleavage: None; Specific Gravity: 2.8–3.0

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth surface. This specimen appears potentially vesicular or weathered, formed in volcanic environments.

Uses & Applications

Used primarily in construction for aggregate, road base, railroad ballast, and ground-up for industrial floor tiles or stone wool insulation.

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 the Moon and Mars.

Field Identification & Locations

Identify by its dark color, heavy weight (density), and fine-grained texture. Commonly found in volcanic regions, lava fields, and oceanic ridges.

Identified on: 5/10/2026

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