igneous
Basalt
Basalt
Hardness: 5-6 (Mohs scale); Color: Dark gray to black, often weathering to brown or green; Luster: Dull to sub-metallic; Structure: Fine-grained, often containing small vesicles or gas bubbles; Specific Gravity: 2.8–3.0.
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark gray to black, often weathering to brown or green
- Luster
- Dull to sub-metallic
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark gray to black, often weathering to brown or green; Luster: Dull to sub-metallic; Structure: Fine-grained, often containing small vesicles or gas bubbles; 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, volcanic islands, and flood basalt provinces.
Uses & applications
Extensively used in construction for aggregate in asphalt and concrete, road base, and railroad ballast. Frequently used as a dimension stone for floor tiles and monuments.
Geological facts
Basalt is the most common rock type in Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture. It often shows 'vesicles' (small holes) where gas escaped during cooling.
