igneous
Vesicular basalt (possibly scoriaceous basalt)
Basalt, chiefly plagioclase feldspar, clinopyroxene, and iron-rich minerals; approximate composition 45–52% SiO₂
AI-generated identification · may be incorrectDark gray to greenish-gray, fine-grained, porous, and dull to weakly vitreous; hardness about 5–6, no obvious cleavage, and typical specific gravity 2.7–3.0. The cavities are gas vesicles, some possibly lined or stained by secondary minerals.
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Physical properties
Dark gray to greenish-gray, fine-grained, porous, and dull to weakly vitreous; hardness about 5–6, no obvious cleavage, and typical specific gravity 2.7–3.0. The cavities are gas vesicles, some possibly lined or stained by secondary minerals.
Formation & geological history
An extrusive volcanic rock formed when basaltic lava cooled rapidly at or near the surface, trapping gas bubbles; commonly Quaternary to much older in age depending on locality.
Uses & applications
Used as crushed aggregate, road stone, lightweight landscaping rock, and occasionally as a decorative specimen; generally little jewelry value.
Geological facts
Its abundant vesicles indicate volatile-rich lava or frothy material near a lava flow’s surface. Green coloration may reflect weathering or alteration to chlorite, celadonite, or other secondary minerals.
Field identification & locations
Common in volcanic regions, including Hawaii, Iceland, the Cascades, India’s Deccan Plateau, and oceanic islands. Identify it by its fine texture, irregular holes, and heavy feel; distinguish from pumice because basalt is darker and denser.
