igneous
Scoria
Scoria (Vesicular Basaltic Rock)
Hardness: 5-6 (Mohs); Color: Dark grey, black, or reddish-brown; Luster: Dull/Earthy; Structure: Vesicular (full of holes); Specific Gravity: 2.5-3.0.
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey, black, or reddish-brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey, black, or reddish-brown; Luster: Dull/Earthy; Structure: Vesicular (full of holes); Specific Gravity: 2.5-3.0.
Formation & geological history
Formed from the rapid cooling of gas-rich basaltic or andesitic lava. The holes (vesicles) are created by trapped gas bubbles that escaped as the lava solidified. They are typical of Cenozoic to recent volcanic activity.
Uses & applications
Used in landscaping for decorative ground cover, as drainage rock, in high-temperature gas grills, and as weight in concrete for highway construction.
Geological facts
Scoria is often confused with pumice, but scoria is denser and usually dark in color, whereas pumice is light and floats on water. Many 'lava rocks' sold in stores for BBQ grills are actually scoria.
Field identification & locations
Identify by its dark color and high vesicle (hole) density. Found in volcanic regions like Hawaii, Iceland, and the Pacific Northwest. Collectors should look for unique shapes or color variations near volcanic cones.
