igneous
Scoria
Vesicular Basalt / Scoria
Hardness: 5-6 Mohs. Color: Reddish-brown to dark black. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with holes). Specific gravity: Relatively low due to gas bubbles.
- Hardness
- 5-6 Mohs
- Color
- Reddish-brown to dark black
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish-brown to dark black. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with holes). Specific gravity: Relatively low due to gas bubbles.
Formation & geological history
Formed from the rapid cooling of gas-rich mafic lava (basaltic) expelled during explosive volcanic eruptions. The holes (vesicles) are formed by trapped gas escaping as the lava solidifies.
Uses & applications
Commonly used in landscaping (lava rock), as a lightweight aggregate in concrete, for gas grills, and in high-temperature insulation.
Geological facts
Scoria is often confused with pumice, but scoria is denser and sinks in water, whereas pumice is silica-rich and floats. The reddish color often comes from the oxidation of iron within the lava.
Field identification & locations
Identify by its highly porous, jagged surface and reddish/black color. Commonly found near cinder cones and volcanic fields in places like Iceland, Italy, or the American Southwest.
