igneous
Basalt
Basalt (primarily Plagioclase feldspar and Pyroxene)
Hardness: 6 (Mohs), Color: Dark grey to black, Luster: Dull to sub-metallic (fine-grained), Crystal Structure: Aphanitic (fine-grained), Specific Gravity: 2.8 - 3.0
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Physical properties
Hardness: 6 (Mohs), Color: Dark grey to black, Luster: Dull to sub-metallic (fine-grained), Crystal Structure: Aphanitic (fine-grained), Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. Found in oceanic crust, volcanic islands, and continental flood basalts.
Uses & applications
Used extensively in construction as road base, concrete aggregate, railroad ballast, and for floor tiles or monuments.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floors. It is also found on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, fine-grained texture, and high density. Commonly found in former volcanic regions or areas with tectonic activity.
