igneous
Basalt
Basalt
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic when wet; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic when wet
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic when wet; 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 exposed at or very near the surface of a terrestrial planet or a moon. Common in oceanic crustal plates and hotspots.
Uses & applications
Extensively used in construction for high-quality aggregate, road base, railroad ballast, and dimension stone for pavers or countertops.
Geological facts
Basalt covers more than 90% of all volcanic rock on Earth. It is also the most common rock type on the Moon's surface, forming the lunar maria.
Field identification & locations
Identify by its heavy weight, dark color, and lack of visible crystals to the naked eye. Often found in volcanic regions, riverbeds, and coastal areas as rounded cobbles.
