igneous
Pumice or Scoriaceous Basalt
Vesicular volcanic rock
Hardness: 5-6 (Mohs scale), Color: Brownish-gray, Luster: Dull or earthy, Crystal structure: Amorphous/glassy groundmass with vesicles, Cleavage: None, Specific gravity: Varies, often floats if highly vesicular (pumice) or sinks if basaltic.
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Physical properties
Hardness: 5-6 (Mohs scale), Color: Brownish-gray, Luster: Dull or earthy, Crystal structure: Amorphous/glassy groundmass with vesicles, Cleavage: None, Specific gravity: Varies, often floats if highly vesicular (pumice) or sinks if basaltic.
Formation & geological history
Formed during explosive volcanic eruptions where expanding gases dissolved in molten magma create bubbles (vesicles) that become trapped as the lava rapidly cools and solidifies.
Uses & applications
Used in lightweight aggregate concrete, landscaping, abrasive stones, horticulture, and personal care (e.g., pumice stones for skin exfoliation).
Geological facts
Vesicular rocks often exhibit high porosity due to escaping gases. Scoria is typically darker, denser, and more mafic than lighter, felsic pumice.
Field identification & locations
Easily identified by its characteristic pitted or vesicular texture (full of holes). Commonly found in volcanic regions worldwide.
