igneous
Scoria (Lava Rock)
Vesicular Basalt / Scoria
Hardness: 5-6 (Mohs scale); Color: Black to dark grey; Luster: Dull/Earthy; Structure: Highly vesicular (pitted with air bubbles); Specific Gravity: 0.8 to 2.1 (often floats temporarily)
- Hardness
- 5-6 (Mohs scale)
- Color
- Black to dark grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Black to dark grey; Luster: Dull/Earthy; Structure: Highly vesicular (pitted with air bubbles); Specific Gravity: 0.8 to 2.1 (often floats temporarily)
Formation & geological history
Formed from gas-rich mafic magma cooling rapidly during a volcanic eruption. The 'holes' are created by trapped gas bubbles (vesicles) as the lava solidifies. It is usually from the Cenozoic era or younger in active volcanic regions.
Uses & applications
Commonly used for landscaping (lava rocks), gas grill heating stones, high-temperature insulation, and lightweight concrete aggregate.
Geological facts
Unlike pumice, which is also vesicular, scoria is denser and will usually sink in water eventually. It is a major component of volcanic cinder cones.
Field identification & locations
Identify in the field by its very light weight relative to appearance, rough/sharp texture, and dark color. Common in volcanic fields like those in Hawaii, Iceland, and the Western United States.
