igneous
Basalt
Basalt
Hardness: 6 on Mohs scale; Color: Dark grey to black, brownish on weathered surfaces; Luster: Dull to earthy, fine-grained phaneritic or aphanitic texture; Crystal structure: Aphanitic (microscopic crystals); Cleavage: None, exhibits conchoidal or irregular fracture; Specific gravity: 2.8-3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black, brownish on weathered surfaces
- Luster
- Dull to earthy, fine-grained phaneritic or aphanitic texture
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black, brownish on weathered surfaces; Luster: Dull to earthy, fine-grained phaneritic or aphanitic texture; Crystal structure: Aphanitic (microscopic crystals); Cleavage: None, exhibits conchoidal or irregular fracture; Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or moon. Typically found in volcanic environments such as mid-ocean ridges, hotspot shield volcanoes, and continental flood basalts.
Uses & applications
Widely used in construction as crushed stone for concrete aggregate, road base, asphalt paving, and railroad ballast. Also used as dimension stone for tiles and cobblestones, and in the manufacturing of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust, covering majority of the ocean floors. It is also extremely common on the Moon (forming the lunar maria) and Mars (forming Olympus Mons).
Field identification & locations
Identified by its fine-grained, dark grey to black appearance and heavy density. It is often non-porous unless vesicular. Commonly found in areas of past or present volcanism.
