igneous
Possible iron-rich pebble or weathered basalt
Indeterminate; likely iron-stained mafic rock, possibly basalt
AI-generated identification · may be incorrectSmall rounded, dark brown-black specimen with a dull to slightly glassy luster and apparent fine-grained texture. Hardness is likely about 5–6.5 Mohs; cleavage is absent, but density and magnetism cannot be determined from the image.
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Physical properties
Small rounded, dark brown-black specimen with a dull to slightly glassy luster and apparent fine-grained texture. Hardness is likely about 5–6.5 Mohs; cleavage is absent, but density and magnetism cannot be determined from the image.
Formation & geological history
If basalt, it formed when iron- and magnesium-rich lava cooled rapidly at or near Earth’s surface, commonly in Cenozoic or older volcanic terrains. The brown coloration likely reflects surface oxidation and weathering.
Uses & applications
Common basalt has uses as aggregate, ballast, road stone, and occasionally decorative material; this tiny specimen has primarily educational or collecting value.
Geological facts
The photograph is insufficient for a confident species identification; the specimen could also be an iron-rich concretion, slag, or another dark mineral-bearing pebble. A magnet, streak test, and fresh broken surface would be useful.
Field identification & locations
Look for a dark fine-grained interior, no obvious layers, and possible weak magnetism. Common sources include volcanic regions, gravel deposits, beaches, and glacial tills; test streak on unglazed porcelain and avoid assuming it is a meteorite without laboratory analysis.
