igneous
Basalt (Vesicular)
Basalt (Mafic volcanic rock)
Hardness: 5-6 Mohs. Color: Dark gray to black, often weathering to brown or olive. Luster: Dull/Earthy. Structure: Fine-grained (aphanitic) with small pits or cavities (vesicles). Specific Gravity: 2.8–3.0.
- Hardness
- 5-6 Mohs
- Color
- Dark gray to black, often weathering to brown or olive
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Dark gray to black, often weathering to brown or olive. Luster: Dull/Earthy. Structure: Fine-grained (aphanitic) with small pits or cavities (vesicles). 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. This specimen appears scoriaceous or vesicular, which occurs when gases escape during cooling.
Uses & applications
Used primarily as crushed stone for road base, concrete aggregate, railroad ballast, and sometimes as 'lava rock' for landscaping or filtration.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up the majority of the ocean floor. It is also found extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (density), and lack of visible large crystal grains. Common in volcanic regions such as the Pacific Northwest, Hawaii, and Iceland.
