igneous
Vesicular basalt (likely scoriaceous basalt)
Basalt; primarily plagioclase, pyroxene, and iron-rich olivine, with abundant vesicles
AI-generated identification · may be incorrectDark reddish-brown to black, rough, highly vesicular, and generally dull to slightly glassy; hardness about 5–6 Mohs, fine-grained, with no obvious cleavage. The large central cavity and oxidized red surface are typical of volcanic scoria or lava.
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Physical properties
Dark reddish-brown to black, rough, highly vesicular, and generally dull to slightly glassy; hardness about 5–6 Mohs, fine-grained, with no obvious cleavage. The large central cavity and oxidized red surface are typical of volcanic scoria or lava.
Formation & geological history
An extrusive igneous rock formed when basaltic lava cooled rapidly at or near the surface, trapping gas bubbles; red coloration commonly results from oxidation of iron. Such lava may be geologically recent, from the Cenozoic or Quaternary, though age cannot be determined from the image.
Uses & applications
Used as lightweight aggregate, drainage and landscaping stone, refractory material, and occasionally as a decorative or aquarium rock; usually low jewelry value.
Geological facts
The specimen appears unusually large and hollow, possibly a lava-tube fragment, volcanic bomb, or vesicular lava flow piece rather than ordinary dense basalt.
Field identification & locations
Identify it by its very low density, abundant irregular holes, angular texture, and basaltic dark composition; common in volcanic regions such as Hawaii, Iceland, Japan, the Cascades, and Mediterranean volcanic fields. A magnet may show weak attraction from iron-bearing minerals.
