igneous
Iron-rich volcanic rock, likely basalt or scoria
Basaltic scoria; primarily plagioclase, pyroxene, and iron oxides
AI-generated identification · may be incorrectDark reddish-purple, fine-grained and porous, with a dull to slightly earthy luster; likely Mohs hardness 5–6, with no visible cleavage and low-to-moderate specific gravity. The rounded shape suggests it may be naturally water-worn or tumbled.
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Physical properties
Dark reddish-purple, fine-grained and porous, with a dull to slightly earthy luster; likely Mohs hardness 5–6, with no visible cleavage and low-to-moderate specific gravity. The rounded shape suggests it may be naturally water-worn or tumbled.
Formation & geological history
Formed when gas-rich basaltic lava cooled rapidly, trapping vesicles; red coloration commonly results from oxidation of iron-bearing minerals. Exact geological age and locality cannot be determined from the image.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive, and decorative material; generally has little jewelry value.
Geological facts
Scoria is vesicular volcanic rock, unlike dense basalt; its pores are usually irregular and larger than those in pumice, and it commonly sinks in water.
Field identification & locations
Identify by testing for irregular vesicles, a streak that may be reddish-brown, and weak attraction to a magnet if magnetite is present. Common worldwide near basaltic volcanoes, including Hawaii, Iceland, Mexico, and western North America.
