igneous
Vesicular Basalt
Extrusive mafic igneous rock
Hardness: 5-6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) with vesicles; Specific gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) with vesicles; 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 Earth's surface. The small holes (vesicles) are created by gas bubbles escaping from the lava as it solidifies.
Uses & applications
Used in construction as road base, concrete aggregate, and railroad ballast. Larger pieces are popular for aquarium landscaping and garden decoration.
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 on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight compared to other light-colored rocks of the same size, and the presence of small pits or holes on the surface. Commonly found in volcanic regions.
