igneous
Rounded river pebble, likely weathered basalt or andesite
Fine-grained volcanic rock; composition commonly plagioclase, pyroxene, and minor iron oxides
AI-generated identification · may be incorrectGray-brown, dull to slightly waxy luster, fine-grained and massive with no visible cleavage; estimated Mohs hardness 5–6 and specific gravity about 2.7–3.1. The rounded shape and surface pitting indicate water abrasion and weathering.
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Physical properties
Gray-brown, dull to slightly waxy luster, fine-grained and massive with no visible cleavage; estimated Mohs hardness 5–6 and specific gravity about 2.7–3.1. The rounded shape and surface pitting indicate water abrasion and weathering.
Formation & geological history
Formed when volcanic lava cooled rapidly at or near Earth’s surface, then was transported and rounded in a stream or shoreline environment. Exact age and identity cannot be determined from the image alone.
Uses & applications
Typically used as decorative landscaping stone, aquarium gravel, craft material, or a paperweight; it has little jewelry value unless unusually attractive or historically significant.
Geological facts
Basaltic pebbles commonly develop iron-oxide brown coloration and vesicular pits during weathering. A streak, magnet test, fresh fracture, and hand lens would improve identification.
Field identification & locations
Common in volcanic terrains and river deposits worldwide; likely locations include the Pacific Northwest, Iceland, Hawaii, and other basalt-bearing regions. Estimated value: $0–$5 as an ordinary pebble, occasionally $5–$20 as a labeled specimen.
