igneous
Vesicular Basalt
Basalt (Mafic volcanic rock)
Hardness: 5-6 Mohs. Color: Dark gray to black, often weathered to reddish-brown. Luster: Dull to earthy. Structure: Vesicular (containing gas bubbles/holes). Specific Gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- Dark gray to black, often weathered to reddish-brown
- Luster
- Dull to earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Dark gray to black, often weathered to reddish-brown. Luster: Dull to earthy. Structure: Vesicular (containing gas bubbles/holes). Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. These specific specimens likely date from the Cenozoic era, common in volcanic fields.
Uses & applications
Used primarily in construction (crushed stone, road base), landscaping, and as heat-resistant materials for fireplaces and saunas due to its thermal mass.
Geological facts
The holes (vesicles) are formed by gas bubbles that were trapped in the lava as it cooled. Basalt is the most common rock type in the earth's crust and makes up most of the ocean floor.
Field identification & locations
Identify by its dark color, heavy weight compared to other rocks, and the presence of small pits or holes. Commonly found in volcanic regions like the Pacific Northwest, Hawaii, or Iceland.
