igneous
Basalt
Basalt
Hardness: 5-6 (Mohs scale), Color: Dark gray to black, Luster: Dull to subvitreous, Crystal structure: Fine-grained (aphanitic) or glassy, Cleavage: None, Specific gravity: 2.9-3.1
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Physical properties
Hardness: 5-6 (Mohs scale), Color: Dark gray to black, Luster: Dull to subvitreous, Crystal structure: Fine-grained (aphanitic) or glassy, Cleavage: None, Specific gravity: 2.9-3.1
Formation & geological history
Formed from the rapid cooling of basaltic lava at or near the Earth's surface. Extrusive igneous rock.
Uses & applications
Used in construction, as aggregate, in road building, and for making stone wool (basalt fiber).
Geological facts
Basalt is the most common volcanic rock on Earth, comprising most of the ocean floor.
Field identification & locations
Identify by its dark color, fine-grained texture, and sometimes vesicular (porous) appearance. Very common worldwide.
