igneous
Basalt (Weathered)
Mafic Igneous Rock
Hardness (6 on Mohs scale), dark grey to greenish-black color, dull luster, fine-grained (aphanitic) texture, specific gravity of 2.8-3.0
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Physical properties
Hardness (6 on Mohs scale), dark grey to greenish-black color, dull luster, fine-grained (aphanitic) texture, specific gravity of 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near a planetary surface. Commonly found in volcanic provinces.
Uses & applications
Used primarily in construction as aggregate, for making asphalt, and in industrial stone casting (basalt fiber).
Geological facts
Basalt is the most common rock type in the Earth's crust and also makes up most of the ocean floors and the lunar maria on the Moon.
Field identification & locations
Identify by its dark color, heavy weight for its size, and lack of visible large crystals. Commonly found in areas with historic volcanic activity.
