igneous
Scoria (vesicular volcanic rock)
Basaltic scoria; chiefly plagioclase, pyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectTypically reddish-brown to black, highly vesicular, dull to slightly glassy, and lightweight; hardness about 5–6 Mohs, with irregular fractures and no cleavage. The cavities are gas bubbles preserved in lava.
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Physical properties
Typically reddish-brown to black, highly vesicular, dull to slightly glassy, and lightweight; hardness about 5–6 Mohs, with irregular fractures and no cleavage. The cavities are gas bubbles preserved in lava.
Formation & geological history
Forms when gas-rich basaltic magma erupts and rapidly cools, commonly in cinder cones and lava flows. It is generally geologically young, ranging from recent eruptions to rocks millions of years old.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, abrasive, and in concrete or cinder blocks; usually little jewelry value.
Geological facts
The red color commonly results from oxidation of iron during or after eruption. It differs from pumice because scoria is darker, denser, and usually has larger, less interconnected vesicles.
Field identification & locations
Identify it by its rough, bubbly texture, dark reddish color, and low density, while distinguishing it from artificial lightweight concrete by its natural irregular vesicles and mineral texture. Common around basaltic volcanoes worldwide, including Iceland, Hawaii, Italy, Mexico, and the western United States.
