igneous
Basalt River Pebble
Basalt (Aphanitic Mafic Volcanic Rock)
Hardness: 6 (Mohs), Color: Dark grey to charcoal, Luster: Dull/Earthy, Crystal Structure: Aphanitic (fine-grained), Cleavage: None, Specific Gravity: 2.8 - 3.0
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Physical properties
Hardness: 6 (Mohs), Color: Dark grey to charcoal, Luster: Dull/Earthy, 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 or very near the Earth's surface. This specific specimen has been rounded by fluvial (water) erosion.
Uses & applications
Commonly used as crushed stone in construction, road base, and as decorative river rock in landscaping.
Geological facts
Basalt is the most common rock in Earth's crust and makes up most of the ocean floor. It is also common on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, fine-grained texture, and significant weight for its size. Often found in riverbeds or near volcanic zones.
