igneous
Reddish vesicular volcanic rock (likely scoria)
Scoria, a vesicular basaltic to andesitic lava; predominantly plagioclase, pyroxene, and iron-bearing volcanic glass
AI-generated identification · may be incorrectTypically dark red-brown to black, highly vesicular, rough, and dull to slightly vitreous; hardness about 5–6 Mohs, with no consistent cleavage and low-to-moderate specific gravity. The reddish color reflects oxidation of iron during or after eruption.
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Physical properties
Typically dark red-brown to black, highly vesicular, rough, and dull to slightly vitreous; hardness about 5–6 Mohs, with no consistent cleavage and low-to-moderate specific gravity. The reddish color reflects oxidation of iron during or after eruption.
Formation & geological history
Forms when gas-rich basaltic or andesitic lava rapidly cools, trapping bubbles; red surfaces commonly develop in oxidizing conditions near cinder cones or lava flows. Most examples are Cenozoic or younger, though scoria occurs throughout geologic time.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, abrasive, and in lightweight concrete; generally not used as a gemstone.
Geological facts
Scoria is denser and commonly darker than pumice, whose abundant connected pores can make it float. The specimen’s irregular cavities and oxidized red color are characteristic of weathered volcanic cinder.
Field identification & locations
Identify by its frothy cavities, very rough surface, low weight, and streak-free or weakly reddish powder; common localities include volcanic fields in Iceland, Italy, Mexico, Hawaii, and the western United States.
