igneous
Vesicular basalt (scoriaceous volcanic rock)
Scoria; iron-rich vesicular basalt, primarily plagioclase, pyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectDark reddish-brown, highly vesicular, dull to slightly glassy luster, fine-grained groundmass, and typically no visible cleavage; hardness about 5–6 Mohs, specific gravity roughly 2.0–2.8. The rusty color commonly reflects oxidation of iron-bearing minerals.
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Physical properties
Dark reddish-brown, highly vesicular, dull to slightly glassy luster, fine-grained groundmass, and typically no visible cleavage; hardness about 5–6 Mohs, specific gravity roughly 2.0–2.8. The rusty color commonly reflects oxidation of iron-bearing minerals.
Formation & geological history
Forms when basaltic lava cools rapidly at or near the surface, trapping expanding gas bubbles; oxidation may occur during or after emplacement. It is generally young in geological terms, commonly Cenozoic or younger, though older examples exist.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive, and occasionally in construction or horticultural drainage; generally not suitable for fine jewelry.
Geological facts
Scoria is denser and darker than pumice, while vesicles are usually larger and more irregular. The specimen may also be an oxidized lava fragment or volcanic bomb.
Field identification & locations
Identify it by its porous texture, reddish-black basaltic color, and lack of sedimentary layering; a streak test, low density, and association with volcanic terrain are useful clues. Common worldwide near basaltic volcanoes, especially Hawaii, Iceland, Italy, and the western United States.
