igneous
Basalt
Basalt (Mafic Extrusive Igneous Rock)
Hardness: 6-7 on Mohs scale; Color: Dark grey, brownish-grey to black; Luster: Dull, earthy, sub-metallic; Texture: Aphanitic (fine-grained), vesicular with small gas cavities; Composition: Rich in plagioclase feldspar and pyroxene.
- Hardness
- 6-7 on Mohs scale
- Color
- Dark grey, brownish-grey to black
- Luster
- Dull, earthy, sub-metallic
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Dark grey, brownish-grey to black; Luster: Dull, earthy, sub-metallic; Texture: Aphanitic (fine-grained), vesicular with small gas cavities; Composition: Rich in plagioclase feldspar and pyroxene.
Formation & geological history
Formed from the rapid cooling of mafic lava rich in iron and magnesium at or near the Earth's surface. Common in volcanic regions, oceanic crust, and continental flood basalt provinces.
Uses & applications
Extensively used in construction as crushed stone for concrete aggregate, road base, asphalt, and railroad ballast. Also used for dimension stone and stone carving.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up most of the ocean floors. It is also found in abundance on the Moon and Mars, forming the lunar maria.
Field identification & locations
Identified by its dark color, heavy weight due to iron content, and fine-grained texture often featuring small holes (vesicles) formed by escaping gas during cooling. Found widely in volcanic areas.
