igneous
Scoria (vesicular basalt)
Basaltic scoria; chiefly plagioclase, clinopyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectDark brown to black, highly vesicular, rough, and usually glassy to dull; hardness about 5–6 Mohs, no obvious cleavage, and relatively low density due to abundant gas cavities.
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Physical properties
Dark brown to black, highly vesicular, rough, and usually glassy to dull; hardness about 5–6 Mohs, no obvious cleavage, and relatively low density due to abundant gas cavities.
Formation & geological history
An extrusive volcanic rock formed when gas-rich basaltic lava cooled rapidly, trapping bubbles. It commonly formed during Quaternary volcanic eruptions, though scoria occurs in volcanic terrains of many ages.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, abrasive, and decorative rock; attractive pieces are collected but generally have modest value.
Geological facts
Scoria is denser and darker than pumice because its basaltic melt contains more iron and magnesium. The specimen’s weathered brown surface may reflect oxidation of iron-bearing minerals.
Field identification & locations
Identify it by its dark color, abundant irregular vesicles, rough texture, and heaviness compared with pumice. Common around cinder cones and basaltic lava fields, including Iceland, Hawaii, Mexico, and western North America.
