igneous
Rounded reddish-brown river cobble, likely weathered granite or granitic gneiss
Feldspar–quartz–mica rock; exact identification requires a fresh surface or testing
AI-generated identification · may be incorrectFine-to-medium granular texture with reddish-brown iron staining, scattered dark mica/amphibole, and possible quartz; likely Mohs 6–7, nonmetallic luster, massive structure, and no obvious cleavage as a whole rock.
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Physical properties
Fine-to-medium granular texture with reddish-brown iron staining, scattered dark mica/amphibole, and possible quartz; likely Mohs 6–7, nonmetallic luster, massive structure, and no obvious cleavage as a whole rock.
Formation & geological history
Probably formed from slowly cooled Precambrian-to-young continental granite, then liberated by weathering and rounded by river or beach transport; the brown color reflects oxidation of iron-bearing minerals.
Uses & applications
Suitable mainly as a curio, paperweight, landscaping stone, or educational specimen; not generally valuable for jewelry or construction in this small form.
Geological facts
The smooth shape indicates prolonged abrasion, while the dark seam may be a mafic mineral-rich band, fracture fill, or weathering feature rather than a distinct mineral.
Field identification & locations
Look for visible interlocking quartz and feldspar grains, hardness sufficient to scratch glass, and lack of reaction to dilute hydrochloric acid; common in granitic terrains and stream gravels worldwide.
