igneous
Basalt
Mafic volcanic rock (Basalt)
Hardness (Mohs): 6.0; Color: Dark grey to black; Luster: Dull/Sub-metallic; Structure: Fine-grained/Aphanitic, often vesicular (pitted); Specific Gravity: 2.8–3.0
- Color
- Dark grey to black
- Luster
- Dull/Sub-metallic
Identified More igneous →
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Physical properties
Hardness (Mohs): 6.0; Color: Dark grey to black; Luster: Dull/Sub-metallic; Structure: Fine-grained/Aphanitic, often vesicular (pitted); Specific Gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron at or very near the Earth's surface. Found in oceanic crust and continental flood basalt provinces.
Uses & applications
Used in construction, road base, concrete aggregate, railroad ballast, and ground for high-quality insulation (stone wool).
Geological facts
Basalt is the most common rock type in the Earth's crust and also makes up the lunar maria on the Moon and the surface of Mars and Venus.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture. It often shows small holes (vesicles) where gas was trapped. Extremely abundant globally.
