igneous
Basalt
Basalt
Hardness: 6.0; Color: Dark gray to black; Luster: Dull to earthy; Crystal structure: Aphanitic (fine-grained), often containing plagioclase feldspar and pyroxene; Specific gravity: 2.8-3.0.
- Hardness
- 6
- Color
- Dark gray to black
- Luster
- Dull to earthy
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Physical properties
Hardness: 6.0; Color: Dark gray to black; Luster: Dull to earthy; Crystal structure: Aphanitic (fine-grained), often containing plagioclase feldspar and pyroxene; 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 rock in Earth's crust.
Uses & applications
Extensively used in construction, especially as road base, railroad ballast, and aggregate in concrete. Also used for high-quality floor tiles and landscape stone.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up most of the surface of the Moon, Mars, and Venus. The famous Giant's Causeway in Northern Ireland consists of columnar basalt.
Field identification & locations
Identify in the field by its dark color, heavy weight (density), and fine-grained texture. It often shows a conchoidal or irregular fracture. Commonly found in lava flows and oceanic crust.
