igneous
Weathered brown pebble, possibly basalt or iron-rich chert
Provisional identification: fine-grained basalt (plagioclase–pyroxene), potentially coated by iron oxides; exact identification requires testing
AI-generated identification · may be incorrectDark brown, rounded and water-worn, with dull to weakly glossy luster and small pits or vesicles; likely hardness about 5–6 and no obvious cleavage. The smooth surface and dense appearance are consistent with basalt, though chert or iron-rich sedimentary rock is also possible.
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Physical properties
Dark brown, rounded and water-worn, with dull to weakly glossy luster and small pits or vesicles; likely hardness about 5–6 and no obvious cleavage. The smooth surface and dense appearance are consistent with basalt, though chert or iron-rich sedimentary rock is also possible.
Formation & geological history
Likely formed as a volcanic basaltic lava rock and later rounded by stream or beach abrasion; basalt commonly ranges from Cenozoic to Precambrian in age. Iron-oxide weathering may produce the brown coloration.
Uses & applications
Primarily a natural curiosity, teaching specimen, or landscaping pebble; not generally valuable for jewelry or industrial use at this size.
Geological facts
Basalt is the most abundant volcanic rock on Earth and forms much of the oceanic crust. Vesicles, if present, are gas bubbles preserved during lava cooling.
Field identification & locations
Check for a very fine-grained texture, faint magnetic response, and a dark gray interior beneath the brown weathering rind; a glassy fracture and conchoidal break would instead suggest chert. Common in volcanic regions, river gravels, and beaches.
