igneous
Vesicular scoria (likely iron-rich volcanic scoria)
Scoria, typically basaltic to andesitic; chiefly plagioclase, pyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectDark orange-brown, highly vesicular, dull to earthy luster, irregular massive texture, and no cleavage; hardness about 5–6 Mohs, though weathering makes the surface friable. Low density and abundant gas cavities are diagnostic.
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Physical properties
Dark orange-brown, highly vesicular, dull to earthy luster, irregular massive texture, and no cleavage; hardness about 5–6 Mohs, though weathering makes the surface friable. Low density and abundant gas cavities are diagnostic.
Formation & geological history
Forms when gas-rich basaltic or andesitic lava rapidly cools, trapping bubbles; the orange color commonly reflects oxidation of iron-bearing minerals. Usually Quaternary to recent around cinder cones, lava flows, and volcanic vents.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, abrasive, and occasionally in cement products; generally not a jewelry gemstone.
Geological facts
Scoria is denser and generally darker than pumice, whose pores are finer and whose overall density may be low enough to float. Vesicles form from expanding dissolved volcanic gases during eruption.
Field identification & locations
Identify it by its rough, frothy surface, abundant irregular holes, angular breakage, and lightweight feel; common in volcanic regions such as Iceland, the western United States, Mexico, Italy, and Japan.
