igneous
Basalt
Basalt (Mafic Volcanic Rock)
Hardness: 5-6 (Mohs); Color: Dark gray to black; Luster: Dull or earthy; Crystal Structure: Aphanitic (fine-grained); Cleavage: Non-existent; Specific Gravity: 2.8–3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark gray to black
- Luster
- Dull or earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark gray to black; Luster: Dull or earthy; Crystal Structure: Aphanitic (fine-grained); Cleavage: Non-existent; 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 commonly found at mid-ocean ridges or volcanic hotspots.
Uses & applications
Extensively used in construction as aggregate (crushed stone), for concrete and asphalt, and occasionally for high-durability floor tiles or dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust, covering most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, fine-grained texture, and high density. Commonly found in volcanic regions like Hawaii, Iceland, or the Columbia River Plateau. Use a magnet to check for titanomagnetite grains.
