igneous
Vesicular basalt (likely weathered scoria)
Mafic volcanic rock; chiefly plagioclase, pyroxene, and often olivine, with abundant gas vesicles
AI-generated identification · may be incorrectDark reddish-brown, fine-grained, dull to weakly earthy luster, irregular vesicles, and no obvious cleavage; hardness about 5–6 Mohs, specific gravity typically 2.4–3.0. The reddish color likely reflects oxidation of iron-bearing minerals.
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Physical properties
Dark reddish-brown, fine-grained, dull to weakly earthy luster, irregular vesicles, and no obvious cleavage; hardness about 5–6 Mohs, specific gravity typically 2.4–3.0. The reddish color likely reflects oxidation of iron-bearing minerals.
Formation & geological history
Forms when basaltic lava cools rapidly at or near the surface, trapping bubbles of volcanic gas; the specimen is probably Holocene to older Cenozoic, depending on its locality. Weathering can produce the brown-red surface.
Uses & applications
Used as aggregate, road material, landscaping stone, lightweight construction fill, and occasionally as a decorative or lapidary specimen; generally not jewelry-grade.
Geological facts
Scoria is more vesicular and less dense than ordinary basalt, while dense basalt has fewer visible cavities. The image alone cannot distinguish confidently between weathered basalt, scoria, or a vesicular industrial fragment.
Field identification & locations
Identify by its fine texture, iron-red/brown color, and rounded gas cavities; it should feel stone-like and may scratch glass only weakly or not at all. Common in volcanic regions such as Hawaii, Iceland, western North America, Italy, and Japan.
