igneous
Scoria
Vesicular Basalt / Scoria
Hardness: 5-6 on Mohs scale; Color: Dark brown, black, to reddish-brown; Luster: Earthy to dull; Texture: Vesicular (full of cavities/bubbles); Density: Low, floats temporarily or sinks slowly due to trapped air spaces.
- Hardness
- 5-6 on Mohs scale
- Color
- Dark brown, black, to reddish-brown
- Luster
- Earthy to dull
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Physical properties
Hardness: 5-6 on Mohs scale; Color: Dark brown, black, to reddish-brown; Luster: Earthy to dull; Texture: Vesicular (full of cavities/bubbles); Density: Low, floats temporarily or sinks slowly due to trapped air spaces.
Formation & geological history
Formed during explosive volcanic eruptions when gas-rich basaltic lava erupts into the air, rapidly cooling and trapping escaping gas bubbles inside the solidifying rock.
Uses & applications
Widely used in landscaping as lava rock, in barbecue grills for heat distribution, in lightweight concrete blocks, and as high-friction aggregate for icy roads.
Geological facts
Scoria is often confused with pumice, but scoria is darker and denser because it forms from basaltic or andesitic lava, whereas pumice forms from silica-rich rhyolitic lava.
Field identification & locations
Identified by its dark, porous, sponge-like surface with visible vesicles. Commonly found in volcanic regions, cinder cones, and lava fields such as those in Hawaii, Iceland, and the American Southwest.
