Basalt (River Stone)

Physical Properties

Hardness: 6.0; Color: Dark grey to black; Luster: Dull; Crystal structure: Aphanitic (fine-grained); 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's surface. This specific specimen has been smoothed by water erosion in a fluvial environment.

Uses & Applications

Used extensively in construction as aggregate, for industrial pavers, and as decorative landscaping stones.

Geological Facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It also exists on the Moon and Mars.

Field Identification & Locations

Identify in the field by its heavy weight, dark color, and lack of visible crystals. Commonly found in riverbeds, volcanic regions, and coastal areas.

Identified on: 5/5/2026

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