igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull to submetallic luster, specific gravity around 2.8-3.0.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull to submetallic luster, specific gravity around 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the Earth's surface, often shaped into a smooth pebble by water action in rivers or beaches.
Uses & applications
Used in construction, road aggregate, railroad ballast, and occasionally in landscaping or hot stone massage therapy.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans, and it is also abundantly found on the Moon and Mars.
Field identification & locations
Commonly found in stream beds, riverbanks, and shorelines worldwide; identifiable by its dark, fine-grained appearance and heavy feel.
