igneous
Basalt Pebble
Aphanitic Igneous Rock
Hardness of 6 on the Mohs scale; dark gray to black color; dull to sub-vitreous luster; fine-grained (aphanitic) crystal structure; no visible cleavage; 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; dull to sub-vitreous luster; fine-grained (aphanitic) crystal structure; no visible cleavage; specific gravity around 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of mafic lava exposed at or very near the Earth's surface, often from volcanic eruptions. Geological age varies widely depending on the deposit.
Uses & applications
Used in construction, aggregate for roads, railroad ballast, and sometimes in landscaping or stonework.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and is also found extensively on the Moon and Mars.
Field identification & locations
Easily identified by its dark, heavy, fine-grained appearance, often rounded into smooth pebbles by water action in rivers or beaches. Common globally.
