igneous
Vesicular Basalt (Scoria)
Aphanitic Mafic Igneous Rock with Vesicular Texture
Hardness: 5-6 Mohs. Color: Reddish-brown to dark brown due to iron oxidation. Luster: Dull/Earthy. Structure: Vesicular (pitted with gas bubbles), fine-grained matrix. Specific Gravity: 2.5-3.0.
- Hardness
- 5-6 Mohs
- Color
- Reddish-brown to dark brown due to iron oxidation
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish-brown to dark brown due to iron oxidation. Luster: Dull/Earthy. Structure: Vesicular (pitted with gas bubbles), fine-grained matrix. Specific Gravity: 2.5-3.0.
Formation & geological history
Formed from rapid cooling of gas-rich basaltic lava at the Earth's surface during volcanic eruptions. The vesicles are formed by trapped gas bubbles. Common in Cenozoic volcanic fields.
Uses & applications
Used in landscaping, high-temperature insulation, gas grill stones, road base, and as a concrete aggregate. Highly valued by collectors for teaching volcanic textures.
Geological facts
The holes (vesicles) are frozen bubbles of gas that escaped while the lava was still molten. If it contains enough vesicles to float on water, it is called pumice, but basaltic versions like this usually sink.
Field identification & locations
Identify by its lightweight feel relative to size, 'swiss cheese' appearance, and rough, abrasive surface. Commonly found near volcanoes in Hawaii, Iceland, and the American Southwest.
