igneous
Basalt Pebble
Basalt
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Matte, Crystal structure: Aphanitic (fine-grained), Specific gravity: 2.8–3.0
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Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Matte, 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 or near the surface of a terrestrial planet or moon. This specimen has been rounded by fluvial or marine erosion.
Uses & applications
Raw basalt is used in construction as aggregate, for road base, and in concrete. Natural river pebbles are used in landscaping and aquariums.
Geological facts
Basalt is the most common rock in Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and absence of visible large crystals. Often found on beaches and in riverbeds near volcanic regions.
