igneous
Vesicular basalt (likely scoria)
Basaltic volcanic rock; primarily plagioclase, pyroxene, and olivine, with abundant vesicles
AI-generated identification · may be incorrectDark brown to black, dull earthy luster, fine-grained and porous with rounded holes; hardness about 5–6 Mohs, no obvious cleavage, and typically dense except where vesicular.
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Physical properties
Dark brown to black, dull earthy luster, fine-grained and porous with rounded holes; hardness about 5–6 Mohs, no obvious cleavage, and typically dense except where vesicular.
Formation & geological history
Formed when basaltic lava cooled rapidly at or near the surface, trapping gas bubbles; generally Cenozoic or younger, though basalt occurs throughout geologic time. The image may show weathered scoria or a small lava fragment.
Uses & applications
Used as lightweight aggregate, landscaping stone, road material, abrasives, and sometimes in decorative collections; generally not suitable for jewelry.
Geological facts
Scoria is commonly more vesicular and lightweight than ordinary basalt, while pumice is usually much lighter and often pale. The specimen’s exact identification requires testing its weight, streak, and texture.
Field identification & locations
Common in volcanic fields, cinder cones, lava flows, and beaches near basaltic volcanoes, including Hawaii, Iceland, the western United States, and oceanic islands. A magnetic response and gray-black powder support basalt; strong fizzing would suggest carbonate instead.
