igneous
Scoria (vesicular volcanic rock)
Basaltic scoria; chiefly plagioclase, pyroxene, olivine, and iron-rich volcanic glass
AI-generated identification · may be incorrectHardness about 5–6 Mohs; dark reddish-brown to black, highly vesicular, generally dull to weakly glassy, with no prominent cleavage. Low density and abundant gas cavities distinguish it from dense basalt.
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Physical properties
Hardness about 5–6 Mohs; dark reddish-brown to black, highly vesicular, generally dull to weakly glassy, with no prominent cleavage. Low density and abundant gas cavities distinguish it from dense basalt.
Formation & geological history
Forms when gas-rich basaltic magma erupts and rapidly cools, trapping bubbles; commonly Quaternary to recent in age around cinder cones and lava fields.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, barbecue media, and abrasive or decorative material; rarely a jewelry specimen.
Geological facts
Its red-brown color commonly results from oxidation of iron-bearing minerals during or after eruption. The pictured specimen may include attached denser basalt or weathering crust.
Field identification & locations
Identify by its rough, lightweight, porous texture and dark volcanic composition; common in volcanic regions such as Hawaii, Iceland, the western United States, Mexico, and Italy. It is not pumice, which is usually much lighter and more silica-rich.
