Basalt River Stone

Physical Properties

Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull or matte; Crystal structure: Aphanitic (fine-grained, crystals not visible to the naked eye); 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 rounded and smoothed by fluvial or coastal erosion.

Uses & Applications

Commonly used as decorative garden stones, in hot stone massage therapy, as structural aggregate in construction, and for paving.

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 extensively on the Moon and Mars.

Field Identification & Locations

Identify by its dark color, heavy weight for its size (high density), and lack of visible crystals. Commonly found in riverbeds, beaches, and volcanic fields.

Identified on: 5/3/2026

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