igneous
Scoria (vesicular volcanic rock)
Scoria; mafic to intermediate vesicular volcanic rock, commonly basaltic or andesitic
AI-generated identification · may be incorrectDark gray to black, rough and highly vesicular, with a dull to subvitreous luster. Typically composed of plagioclase, pyroxene and sometimes olivine; hardness about 5–6 on Mohs scale, with no prominent cleavage and variable density. Exact mineralogy cannot be confirmed from the image.
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Physical properties
Dark gray to black, rough and highly vesicular, with a dull to subvitreous luster. Typically composed of plagioclase, pyroxene and sometimes olivine; hardness about 5–6 on Mohs scale, with no prominent cleavage and variable density. Exact mineralogy cannot be confirmed from the image.
Formation & geological history
Forms when gas-rich lava cools rapidly, trapping bubbles as vesicles. It is generally geologically young and occurs around volcanic vents, cinder cones and lava flows.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material and abrasive; attractive pieces are collected, but it is rarely used as a gemstone.
Geological facts
Scoria’s holes are frozen gas bubbles, and it is usually denser and less frothy than pumice.
Field identification & locations
Identify it by its dark color, abundant irregular cavities and rough texture; common in volcanic regions worldwide, including basaltic fields and cinder cones. The image is consistent with scoria, though a photo cannot confirm composition.
