igneous
Scoria (volcanic cinder)
Scoria, vesicular basaltic-to-andesitic volcanic rock
AI-generated identification · may be incorrectDark brown to black, rough and highly vesicular, with a generally dull to submetallic luster; composed mainly of volcanic glass and plagioclase, pyroxene, and/or olivine. Hardness is typically about 5–6 Mohs; the pictured specimen’s small size limits confident identification.
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Physical properties
Dark brown to black, rough and highly vesicular, with a generally dull to submetallic luster; composed mainly of volcanic glass and plagioclase, pyroxene, and/or olivine. Hardness is typically about 5–6 Mohs; the pictured specimen’s small size limits confident identification.
Formation & geological history
Forms when gas-rich lava cools rapidly, trapping bubbles in the solidifying rock; commonly produced at cinder cones and lava flows during geologically recent eruptions.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and in some construction products; modest specimens may be kept in rock collections.
Geological facts
Scoria’s abundant gas-bubble cavities distinguish it from denser basalt, though it is less uniformly frothy and typically heavier than pumice.
Field identification & locations
Look for a dark color, rough texture, and irregular holes; it is common in volcanic regions such as the western United States, Iceland, and Hawaii. A photograph cannot establish its exact composition or locality.
