igneous
Vesicular basalt (likely weathered scoria)
Basaltic volcanic rock; chiefly plagioclase, pyroxene, and iron-rich olivine
AI-generated identification · may be incorrectDark gray to brown, highly vesicular, dull to faintly glassy and fine-grained; hardness about 5–6 Mohs, with no obvious cleavage and low-to-moderate specific gravity due to abundant gas bubbles.
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Physical properties
Dark gray to brown, highly vesicular, dull to faintly glassy and fine-grained; hardness about 5–6 Mohs, with no obvious cleavage and low-to-moderate specific gravity due to abundant gas bubbles.
Formation & geological history
Extrusive igneous rock formed when basaltic lava cooled rapidly at or near the surface, trapping volcanic gases; commonly Quaternary to recent, though basalt occurs throughout geologic time.
Uses & applications
Used as lightweight aggregate, landscaping stone, road material, and occasionally as a decorative or teaching specimen; this small weathered fragment has minimal commercial value.
Geological facts
The holes are vesicles formed by escaping or trapped gas, and weathering has produced the pale, rusty surface coating. It may be scoria if strongly reddish and lightweight, or vesicular basalt if relatively dense and dark.
Field identification & locations
Identify it by its porous texture, fine grain, dark basaltic interior, and lack of sedimentary layering or visible large crystals; common in volcanic fields, lava flows, cinder cones, and oceanic islands.
