igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6 on Mohs scale; Color: dark grey to black or brownish; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic) due to rapid cooling; Specific gravity: 2.8–3.0.
- Hardness
- 6 on Mohs scale
- Color
- dark grey to black or brownish
- Luster
- dull to sub-metallic
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Physical properties
Hardness: 6 on Mohs scale; Color: dark grey to black or brownish; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic) due to rapid cooling; 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 a moon. Most common in oceanic crust and volcanic hotspots.
Uses & applications
Extensively used in construction for aggregate, road base, concrete, and railroad ballast. Also used for high-quality stone tiles and floorings.
Geological facts
Basalt is the most common rock on Earth's surface and makes up most of the ocean floor. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight for its size, and absence of large visible crystals. Found globally in volcanic regions like Hawaii, Iceland, and the Deccan Traps.
