igneous
Lava Rock
Basalt / Scoria
Hardness: 5-6 on the Mohs scale. Color: Dark brown, black, dark gray, or reddish. Luster: Dull to vitreous. Crystal structure: Aphanitic (fine-grained) with prominent vesicular texture (numerous gas bubbles/cavities). Specific gravity: 2.0-2.8.
- Hardness
- 5-6 on the Mohs scale
- Color
- Dark brown, black, dark gray, or reddish
- Luster
- Dull to vitreous
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Physical properties
Hardness: 5-6 on the Mohs scale. Color: Dark brown, black, dark gray, or reddish. Luster: Dull to vitreous. Crystal structure: Aphanitic (fine-grained) with prominent vesicular texture (numerous gas bubbles/cavities). Specific gravity: 2.0-2.8.
Formation & geological history
Formed during volcanic eruptions when gas-rich mafic lava rapidly cools and solidifies near the surface, trapping gas bubbles within the rock structure. Usually of recent to ancient volcanic activity, ranging from Holocene to millions of years old.
Uses & applications
Used in landscaping, barbecue grills, aquariums, filtration systems, spa treatments (massage stones), and lightweight construction aggregates.
Geological facts
Scoria is similar to pumice, but it has a darker color, denser composition, and larger vesicles, and it typically sinks in water unlike floating pumice.
Field identification & locations
Easily identified by its dark color, rough texture, and distinctive vesicular holes (gas cavities). Found globally near active or extinct volcanic regions, particularly volcanic islands, cinder cones, and basaltic lava flows.
