Basalt River Stone

Physical Properties

Hardness: 6.0-7.0 (Mohs); Color: Dark grey to charcoal black; Luster: Dull to sub-metallic when polished; 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 the surface of a planet or moon. This specific specimen has been further shaped and smoothed by fluvial (river) erosion over many years.

Uses & Applications

Commonly used as decorative landscaping stones, massage stones (hot stones), in construction as crushed aggregate, and for making cast basalt liners for heavy industry.

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, Mars, and Venus.

Field Identification & Locations

Identify by its heavy weight, dark color, and lack of visible crystals. Commonly found in riverbeds, coastlines near volcanic activity, and volcanic fields. Collectors look for stones with interesting shapes or contrasting mineral veins.

Identified on: 4/20/2026

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