igneous
Basalt with minor mineral crusting
Sideromelane / Extrusive Igneous Rock
Hardness: 6 (Mohs scale), Color: Dark grey to black with brown weathered exterior, Luster: Dull/Earthy, Crystal Structure: Aphanitic (fine-grained), Cleavage: None
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Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black with brown weathered exterior, Luster: Dull/Earthy, Crystal Structure: Aphanitic (fine-grained), Cleavage: None
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. Common in volcanic regions and ocean floor crust.
Uses & applications
Primary use in construction (aggregate, asphalt, railroad ballast), industrial stone wool production, and occasionally used as a decorative landscape stone.
Geological facts
Basalt is the most common rock type on Earth's crust and even makes up much of the surface of the Moon, Mars, and Venus.
Field identification & locations
Identify in the field by its heavy weight (high density), dark color, and fine-grained texture. It often shows weathered brownish rinds when exposed to oxygen.
