igneous
Scoria
Vesicular Basalt / Scoria
Dark gray to black color, highly vesicular texture (porous with many small cavities), dull to sub-metallic luster, Mohs hardness 5 to 6, relatively lightweight compared to dense basalt.
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Physical properties
Dark gray to black color, highly vesicular texture (porous with many small cavities), dull to sub-metallic luster, Mohs hardness 5 to 6, relatively lightweight compared to dense basalt.
Formation & geological history
Formed during explosive volcanic eruptions when gas-rich mafic lava rapidly cools and traps expanding gas bubbles (vesicles) before solidification.
Uses & applications
Widely used in landscaping as decorative lava rock, as an abrasive in pumice soaps, in lightweight concrete aggregate, and in barbecue gas grills.
Geological facts
Unlike lighter-colored pumice, scoria has thicker vesicle walls and higher iron content, which usually causes it to sink in water rather than float.
Field identification & locations
Identified by its distinctive sponge-like porous surface and dark black to reddish-brown coloration. Common in volcanic regions such as Hawaii, Iceland, and the American Southwest.
