igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Fine-grained/Aphanitic; Specific Gravity: 2.8–3.0.
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Fine-grained/Aphanitic; 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.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and decorative garden stones. High-quality basalt is used for stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (density), and lack of visible large crystals. Common in volcanic regions like Hawaii, Iceland, and the Pacific Northwest.
