igneous
Scoria (vesicular basalt)
Basaltic scoria; predominantly plagioclase, pyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectHardness about 5–6 Mohs; dark brown to black, highly vesicular, and usually dull to slightly glassy. It has abundant irregular gas cavities, a fine-grained matrix, no prominent cleavage, and a typical specific gravity of roughly 2.0–2.5.
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Physical properties
Hardness about 5–6 Mohs; dark brown to black, highly vesicular, and usually dull to slightly glassy. It has abundant irregular gas cavities, a fine-grained matrix, no prominent cleavage, and a typical specific gravity of roughly 2.0–2.5.
Formation & geological history
A pyroclastic volcanic rock formed when gas-rich basaltic lava rapidly cooled, trapping bubbles; commonly associated with cinder cones and lava flows, generally Quaternary to Recent in age.
Uses & applications
Used as lightweight aggregate, drainage and landscaping stone, abrasive material, and in horticultural soil mixes; generally not used as a gemstone.
Geological facts
Scoria is denser and typically darker than pumice because its bubbles are less abundant and its iron-rich basaltic composition produces rusty weathering.
Field identification & locations
Identify it by its black-to-reddish color, rough frothy texture, and connected or irregular vesicles; common near basaltic volcanoes worldwide, including Iceland, Hawaii, Italy, and the western United States.
