igneous
Vesicular Basalt
Basalt (Mafic Extrusive Igneous Rock)
Hardness: 5-6 (Mohs scale); Color: Dark grey to black, greenish-grey; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic) with small vesicles (holes/gas bubbles); Specific Gravity: 2.9-3.1
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark grey to black, greenish-grey
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark grey to black, greenish-grey; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic) with small vesicles (holes/gas bubbles); Specific Gravity: 2.9-3.1
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The small holes (vesicles) are created by trapped gas bubbles exiting the lava as it solidifies.
Uses & applications
Used extensively in construction as road aggregate, railroad ballast, and in the manufacturing of stone wool insulation. High-quality specimens are used in aquarium decoration and landscaping.
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 the presence of small pits or holes on the surface. Commonly found in volcanic regions, oceanic islands (like Hawaii), and mid-ocean ridges.
