igneous
Vesicular Basalt
Basalt (Mafic Extrusive Volcanic Rock)
Hardness: 5-6 (Mohs); Color: Dark grey to black; Luster: Dull or sub-metallic; Structure: Fine-grained with vesicles (gas bubbles); Cleavage: None; Specific Gravity: 2.8-3.0.
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to black
- Luster
- Dull or sub-metallic
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to black; Luster: Dull or sub-metallic; Structure: Fine-grained with vesicles (gas bubbles); Cleavage: None; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The pits or pores are caused by gas bubbles being trapped in the lava as it solidifies.
Uses & applications
Used as aggregate in construction, road base, concrete, and as decorative stone in landscaping. High-quality basalt is also used for fiber production and cast stone.
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 common on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and characteristic pitted (vesicular) texture. Commonly found in volcanic regions such as Hawaii, Iceland, and the Pacific Northwest.
