Igneous
Scoria (Lava Rock)
Vesicular Basalt / Scoria
Hardness: 5-6 Mohs. Color: Dark brown to black (often weathers to dark red). Luster: Dull/Earthy. Structure: Highly vesicular (pitted with gas bubbles). Specific Gravity: Relatively low/lightweight due to air pockets.
- Hardness
- 5-6 Mohs
- Color
- Dark brown to black (often weathers to dark red)
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Dark brown to black (often weathers to dark red). Luster: Dull/Earthy. Structure: Highly vesicular (pitted with gas bubbles). Specific Gravity: Relatively low/lightweight due to air pockets.
Formation & geological history
Formed through the rapid cooling of basaltic or andesitic lava containing high concentrations of dissolved gas. As the lava erupts, the gas expands and is trapped as the rock solidifies, creating vesicles. It is common in Cenozoic volcanic fields.
Uses & applications
Extensively used in landscaping, gas grills, high-temperature insulation, drainage systems, and as an additive in lightweight concrete. Occasionally used in bead jewelry for essential oil diffusing.
Geological facts
Unlike pumice, scoria is usually denser and will sink in water. It is a major component of volcanic cinder cones. The term scoria comes from the Greek word for 'rust.'
Field identification & locations
Identify by its 'sponge-like' appearance, dark color, and sharp, jagged edges. Found universally in volcanic regions such as Iceland, Hawaii, and the Western United States (e.g., Arizona, California).
