igneous
Scoria (vesicular basalt)
Scoria; mafic volcanic rock composed chiefly of plagioclase, pyroxene, and iron-rich glass
AI-generated identification · may be incorrectTypically dark red-brown to black, with abundant connected vesicles and a dull to subvitreous luster; hardness about 5–6, no prominent cleavage, and specific gravity roughly 2.0–2.8. The reddish color indicates oxidation of iron during or after eruption.
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Physical properties
Typically dark red-brown to black, with abundant connected vesicles and a dull to subvitreous luster; hardness about 5–6, no prominent cleavage, and specific gravity roughly 2.0–2.8. The reddish color indicates oxidation of iron during or after eruption.
Formation & geological history
Forms when gas-rich basaltic lava cools rapidly, trapping bubbles in a frothy texture; commonly Quaternary to recent in age and associated with cinder cones, lava flows, and volcanic fields.
Uses & applications
Used as lightweight aggregate, landscaping rock, drainage material, barbecue stone, and abrasive media; attractive hand specimens are inexpensive collectibles.
Geological facts
Scoria is denser and generally darker than pumice because its bubbles are less abundant and its magma is more mafic and iron-rich.
Field identification & locations
Identify it by its rough, highly vesicular surface, reddish-black color, and relatively heavy feel; common in volcanic regions such as Iceland, Hawaii, Italy, Mexico, and the western United States. The pictured specimen may be weathered or naturally rounded scoria.
