igneous
Pumice (Basaltic/Scoria)
Scoria
Hardness: 5-6 Mohs. Color: dark gray, black, or reddish-brown. Luster: dull to sub-metallic. Texture: vesicular (highly porous with gas bubbles). Specific Gravity: 2.5-3.0.
- Hardness
- 5-6 Mohs
- Color
- dark gray, black, or reddish-brown
- Luster
- dull to sub-metallic
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Physical properties
Hardness: 5-6 Mohs. Color: dark gray, black, or reddish-brown. Luster: dull to sub-metallic. Texture: vesicular (highly porous with gas bubbles). Specific Gravity: 2.5-3.0.
Formation & geological history
Formed during explosive volcanic eruptions from mafic magma. The holes (vesicles) are created by trapped gas bubbles as the lava cools rapidly. Found in volcanic regions of all ages.
Uses & applications
Used in landscaping (lava rocks), as an abrasive in heavy-duty hand cleaners, in concrete production for lightweight aggregates, and for heat insulation.
Geological facts
Unlike white pumice, scoria is denser and usually does not float in water. It is a major component of volcanic cinder cones.
Field identification & locations
Identify by its rough, bubbly surface and dark color. Common near dormant or active volcanoes like those in Iceland, Hawaii, or the Pacific Northwest.
