igneous
Scoria (Vesicular Basalt)
Scoria (Hydrated silicate volcanic rock with iron and magnesium)
Hardness: 5-6 Mohs. Color: Dark brown to black with reddish tints. Luster: Dull to sub-vitreous. Texture: Vesicular (highly porous with gas bubbles). Specific gravity: Low (often floats briefly/feels light).
- Hardness
- 5-6 Mohs
- Color
- Dark brown to black with reddish tints
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 5-6 Mohs. Color: Dark brown to black with reddish tints. Luster: Dull to sub-vitreous. Texture: Vesicular (highly porous with gas bubbles). Specific gravity: Low (often floats briefly/feels light).
Formation & geological history
Formed from the rapid cooling of gas-rich basaltic lava during explosive volcanic eruptions. The cooling happens so fast that gas bubbles (vesicles) are trapped as solid rock forms.
Uses & applications
Used in landscaping (lava rocks), barbecue grills, high-temperature insulation, lightweight concrete aggregate, and as an abrasive in stone-washing jeans.
Geological facts
Scoria is heavier and has thicker vesicle walls than pumice; while pumice comes from silicic magma and is usually light-colored, scoria comes from basaltic magma and is dark.
Field identification & locations
Identify by its dark color, high porosity, and rough, jagged edges. Common in volcanic fields like those in Iceland, Hawaii, and the Western USA (Craters of the Moon).
