igneous
Basalt Scoria
Vesicular Basalt
Hardness: 5-6 Mohs. Color: Black to dark gray. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with gas bubbles). Specific Gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- Black to dark gray
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Black to dark gray. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with gas bubbles). Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from cooling lava containing trapped gases. As the lava erupts and pressure drops, bubbles form and are frozen in place as the rock solidifies. Common in volcanic regions and oceanic crust.
Uses & applications
Used as decorative landscaping stone (often called lava rock), in barbecue grills (heat retention), lightweight aggregate in concrete, and for road construction.
Geological facts
Scoria is a extrusive volcanic rock. Unlike pumice, scoria has larger bubbles and thicker cell walls, and it sinks in water. It is a primary constituent of cinder cones.
Field identification & locations
Identify by its dark color, porous 'sponge-like' appearance, and relatively light weight compared to solid basalt. Found in volcanic fields like those in Iceland, Hawaii, and Arizona.
