igneous
Vesicular volcanic rock, likely scoria
Scoria; typically basaltic to andesitic volcanic rock composed mainly of plagioclase, pyroxene, and volcanic glass
AI-generated identification · may be incorrectDark brown to reddish-brown, highly vesicular, rough, and dull to slightly glassy; hardness about 5–6 Mohs, no prominent cleavage, and relatively low density due to abundant gas cavities. The rusty color likely reflects oxidation of iron-bearing minerals.
Identified More igneous →
Explore Vesicular volcanic rock, likely scoria in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark brown to reddish-brown, highly vesicular, rough, and dull to slightly glassy; hardness about 5–6 Mohs, no prominent cleavage, and relatively low density due to abundant gas cavities. The rusty color likely reflects oxidation of iron-bearing minerals.
Formation & geological history
Forms when gas-rich lava rapidly cools, commonly in cinder cones, lava flows, and volcanic bombs; generally geologically young, ranging from recent eruptions to rocks of any Phanerozoic age. The specimen may also be weathered iron-rich basaltic scoria.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, abrasive, and sometimes in cement products; generally not used as a gemstone. Attractive vesicular pieces have modest collecting value.
Geological facts
Scoria differs from pumice because it is usually darker, denser, and has thicker-walled vesicles; pumice can float, whereas scoria commonly sinks. The irregular cavities record dissolved volcanic gases escaping during eruption.
Field identification & locations
Identify it by its dark oxidized color, abundant connected-looking bubbles, rough texture, and lightweight but not foam-like feel; common near basaltic volcanoes worldwide, including Hawaii, Iceland, Mexico, and the western United States.
