igneous
Scoria
Vesicular Mafic Igneous Rock
Hardness: 5-6 on the Mohs scale; Color: Dark brown, reddish-brown, or black; Luster: Dull; Crystal structure: Aphanitic with abundant vesicles (gas cavities); Cleavage: None; Specific gravity: Varies, often less than 1.0 if it floats, but typically 2.0-2.5 for denser varieties.
- Hardness
- 5-6 on the Mohs scale
- Color
- Dark brown, reddish-brown, or black
- Luster
- Dull
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Physical properties
Hardness: 5-6 on the Mohs scale; Color: Dark brown, reddish-brown, or black; Luster: Dull; Crystal structure: Aphanitic with abundant vesicles (gas cavities); Cleavage: None; Specific gravity: Varies, often less than 1.0 if it floats, but typically 2.0-2.5 for denser varieties.
Formation & geological history
Formed from gas-rich mafic or intermediate lava (such as basalt) that cools rapidly while escaping gases become trapped as bubbles, creating a vesicular texture. Formed during volcanic eruptions.
Uses & applications
Used in landscaping, lightweight aggregate in concrete, gas barbecue grills, and as an abrasive in personal care products like pumice stones.
Geological facts
Unlike pumice which is felsic and typically floats on water, scoria is denser and usually sinks, though both are formed in explosive volcanic settings.
Field identification & locations
Easily identified by its dark color and numerous small, rounded holes (vesicles) resembling a sponge. Found near volcanic fields worldwide.
