igneous
Weathered vesicular basalt
Basalt, chiefly plagioclase and pyroxene with secondary iron oxides and zeolite/calcite fillings
AI-generated identification · may be incorrectFine-grained, dark brown from weathering, dull to subvitreous luster, with abundant small vesicles and pale mineral crusts; hardness about 5–6, generally massive with no cleavage. The rounded shape indicates water abrasion.
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Physical properties
Fine-grained, dark brown from weathering, dull to subvitreous luster, with abundant small vesicles and pale mineral crusts; hardness about 5–6, generally massive with no cleavage. The rounded shape indicates water abrasion.
Formation & geological history
An extrusive volcanic rock formed when basaltic lava cooled rapidly, likely millions to billions of years ago; surface weathering and cavity mineralization occurred later. Common in volcanic terrains and stream or beach gravels.
Uses & applications
Used as aggregate, road stone, riprap, and building stone; attractive polished pieces are collected, though this specimen has modest gem value.
Geological facts
Vesicles are gas bubbles trapped during lava cooling; pale patches may be zeolites, calcite, or weathering products rather than the primary basalt.
Field identification & locations
Identify by its fine texture, high density, iron-brown weathering, and gas cavities; a streak, acid, and hardness test can distinguish carbonate-filled vesicles. Common worldwide in volcanic regions and derived beaches.
