igneous
Vesicular Basalt (Lava Rock)
Vesicular basalt
Hardness: 5-6 Mohs. Color: dark gray to black, often weathering to reddish-brown. Luster: dull, earthy. Texture: vesicular (honeycombed with gas bubbles). Specific gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- dark gray to black, often weathering to reddish-brown
- Luster
- dull, earthy
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Physical properties
Hardness: 5-6 Mohs. Color: dark gray to black, often weathering to reddish-brown. Luster: dull, earthy. Texture: vesicular (honeycombed with gas bubbles). Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava (basaltic) containing high amounts of volatiles (gases). The vesicles are the remains of gas bubbles trapped as the lava solidified.
Uses & applications
Used in landscaping (lava rock), construction aggregate, asphalt, high-temperature insulation, and as a natural abrasive (pumice-like alternatives).
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The vesicles can sometimes be filled with secondary minerals like zeolites, quartz, or calcite to form 'amygdules'.
Field identification & locations
Identify by its dark color, heavy weight (relative to pumice), and distinct holes (vesicles). Found in volcanic regions like Hawaii, Iceland, and the Pacific Northwest.
