igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) to porphyritic; Specific Gravity: 2.8–3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) to porphyritic; 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 (oceanic crust).
Uses & applications
Used primarily in construction (crushed stone, concrete aggregate, road base), industrial applications (stone wool insulation), and occasionally for decorative landscaping or massage stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. Large areas of the lunar surface are also covered in basaltic lava flows, known as lunar maria.
Field identification & locations
Identify by its heavy weight (high density), dark color, and lack of visible crystals to the naked eye. Commonly found in volcanic regions and along riverbeds downstream from volcanic sources.
