igneous
Scoria (vesicular basalt)
Scoria; vesicular mafic volcanic rock, typically basaltic in composition
AI-generated identification · may be incorrectDark gray-brown, highly vesicular, with a dull to slightly glassy luster; hardness about 5–6 Mohs. Composed mainly of plagioclase, pyroxene, olivine, and volcanic glass; lacks prominent cleavage and is relatively lightweight for its size.
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Physical properties
Dark gray-brown, highly vesicular, with a dull to slightly glassy luster; hardness about 5–6 Mohs. Composed mainly of plagioclase, pyroxene, olivine, and volcanic glass; lacks prominent cleavage and is relatively lightweight for its size.
Formation & geological history
Forms when gas-rich basaltic lava erupts and rapidly cools, trapping abundant bubbles. It is generally Quaternary to recent in age and occurs around cinder cones, lava fields, and volcanic vents.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping rock, abrasive, and sometimes in barbecue or fire pits. Collectible value is usually low unless unusually colored or vesicular.
Geological facts
Scoria is denser and commonly darker than pumice, whose bubbles are more abundant and whose texture is often lighter and more frothy.
Field identification & locations
Identify it by its black-to-red color, rough bubbly surface, and volcanic appearance; it commonly occurs in Hawaii, Iceland, the western United States, Italy, and other volcanic regions. Avoid confusing it with industrial slag, which may contain metallic droplets or unnatural glassy surfaces.
