igneous
Basalt
Basalt (High-iron/magnesium silicate rock)
Hardness: 6.0 on Mohs scale; Color: Dark grey to black; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0. Dense and heavy for its size.
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull/Matte
Identified More igneous →
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Physical properties
Hardness: 6.0 on Mohs scale; Color: Dark grey to black; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0. Dense and heavy for its size.
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. Often found in oceanic crust and huge volcanic plateaus.
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and floor tiles. It is also used as 'lava rocks' for grill surfaces and landscaping.
Geological facts
Basalt is the most common rock type in Earth's crust and makes up most of the ocean floors. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify in the field by its dark color, fine grain (individual crystals are usually too small to see with the naked eye), and weight. Often forms hexagonal columns (columnar jointing) in large flows.
