igneous
Rounded volcanic pebble, likely andesite or basalt
Fine-grained andesite–basalt; chiefly plagioclase feldspar and pyroxene, with possible iron oxides
AI-generated identification · may be incorrectGray to pinkish-gray, fine-grained and massive, with dull to slightly satin luster and no visible cleavage; estimated Mohs hardness 5–6. Its smooth, rounded shape reflects abrasion in water or sediment.
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Physical properties
Gray to pinkish-gray, fine-grained and massive, with dull to slightly satin luster and no visible cleavage; estimated Mohs hardness 5–6. Its smooth, rounded shape reflects abrasion in water or sediment.
Formation & geological history
An extrusive igneous rock formed when lava cooled rapidly at or near Earth’s surface, generally during a volcanic episode of uncertain age; later transported and rounded in a stream, beach, or glacial environment.
Uses & applications
Common material for aggregate, road stone, landscaping, and decorative pebbles; this ordinary specimen has little jewelry value.
Geological facts
The pink tones may reflect oxidized iron or minor feldspar, while dark patches may be mafic minerals, weathering, or inclusions. Exact identification requires a fresh surface, streak, density, and thin-section or chemical analysis.
Field identification & locations
Look for a very fine crystalline texture, substantial weight, and lack of fizz with dilute acid; basalt is usually darker and denser, whereas andesite is commonly lighter gray. Volcanic pebbles occur widely in stream gravels and coastal deposits.
