Basalt

Physical Properties

Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); 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

Commonly used as an aggregate in construction projects, for road base, concrete aggregate, and pavement. High-quality specimens are used for stone carving and as tiles.

Geological Facts

Basalt is the most common rock on Earth's surface. Most of the ocean floor is composed of basalt. It is also common on the Moon and Mars.

Field Identification & Locations

Identify by its dark color, heavy weight for its size, and the absence of visible crystals without a magnifying glass. Found in volcanic regions and ocean floors.

Identified on: 5/7/2026

Mode: Standard