igneous
Pumice (Scoria variety)
Scoria (Vesicular Basalt)
Hardness: 5-6 (Mohs scale); Color: dark brown to black; Luster: dull; Crystal structure: amorphous/glassy; Cleavage: none; Specific gravity: 0.8 to 2.1 (often floats in water if Pumice, sinks if Scoria)
- Hardness
- 5-6 (Mohs scale)
- Color
- dark brown to black
- Luster
- dull
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs scale); Color: dark brown to black; Luster: dull; Crystal structure: amorphous/glassy; Cleavage: none; Specific gravity: 0.8 to 2.1 (often floats in water if Pumice, sinks if Scoria)
Formation & geological history
Formed from the rapid cooling of gas-rich basaltic lava. The holes (vesicles) are created by trapped gas bubbles that were frozen in place as the lava solidified. Primarily found in active or extinct volcanic regions.
Uses & applications
Used as an abrasive in cleaning and polishing, as lightweight aggregate in concrete, for landscaping, and in stonewashed jeans production.
Geological facts
Scoria is often confused with pumice; however, scoria has thicker vesicle walls and is denser, generally causing it to sink in water unlike most pumice specimens.
Field identification & locations
Identify by its hole-filled (vesicular) texture and lightweight feel. Commonly found in volcanic fields, cinder cones, and near the edges of lava flows.
