igneous
Scoria (Vesicular Basalt)
Vesicular Basaltic Andesite
Hardness: 5-6 Mohs. Color: Reddish brown to dark grey/black. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with gas bubbles). Specific gravity: Low (often floats briefly/feels light).
- Hardness
- 5-6 Mohs
- Color
- Reddish brown to dark grey/black
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish brown to dark grey/black. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with gas bubbles). Specific gravity: Low (often floats briefly/feels light).
Formation & geological history
Formed from gas-rich basaltic magma cooling rapidly near the surface of a volcano. The gas bubbles (vesicles) are trapped as the lava solidifies. Typically associated with Cenozoic volcanic activity.
Uses & applications
Used in landscaping (lava rocks), high-temperature insulation, drainage stones, gas grills, and as a lightweight aggregate in concrete.
Geological facts
Scoria is different from pumice because it has thicker cell walls and is denser, causing it to sink in water eventually, whereas pumice often floats indefinitely.
Field identification & locations
Identify by its 'Swiss cheese' appearance, lightweight feel, and rough, abrasive texture. Commonly found near cinder cones and basaltic lava flows in volcanic regions like the American Southwest, Iceland, or Italy.
