Basalt River Pebble

Physical Properties

Hardness: 6.0; Color: Dark grey to black; Luster: Dull/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 at the surface. This specific specimen has been further shaped by fluvial or coastal erosion into a smooth, rounded pebble.

Uses & Applications

Commonly used in construction aggregate, road base, and as decorative stone in landscaping. Its durability makes it ideal for architectural cladding.

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

Identified in the field by its dark color, heavy weight compared to similar-sized rocks, and fine-grained texture. Commonly found in volcanic regions, riverbeds, and beaches near oceanic crust boundaries.

Identified on: 5/1/2026

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