igneous
Scoria
Scoria (vesicular basaltic rock)
Hardness: 5-6 Mohs. Color: Reddish-brown to black. Luster: Dull/earthy. Structure: Highly vesicular (honeycombed with holes). Specific gravity: Relatively low due to porosity.
- Hardness
- 5-6 Mohs
- Color
- Reddish-brown to black
- Luster
- Dull/earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish-brown to black. Luster: Dull/earthy. Structure: Highly vesicular (honeycombed with holes). Specific gravity: Relatively low due to porosity.
Formation & geological history
Formed through the rapid cooling of basaltic or andesitic lava containing high amounts of dissolved gases. As the lava erupts, the gases expand and form bubbles (vesicles) which are frozen into the rock as it solidifies.
Uses & applications
Used extensively in landscaping, gas grill lava rocks, high-temperature insulation, drainage systems, and as an abrasive in stone-washed denim production.
Geological facts
Scoria differs from pumice in that it is denser and has larger vesicles with thicker walls. While it is full of air pockets, it is usually heavy enough to sink in water, unlike most pumice.
Field identification & locations
Identify by its weight (lighter than solid basalt but heavier than pumice), sharp edges, and 'swiss cheese' appearance. Commonly found near cinder cones and on the flanks of shield volcanoes like those in Hawaii or Iceland.
