igneous
Rounded quartz-rich cobble
Likely quartzite or felsic igneous rock; predominantly quartz (SiO₂), with feldspar and minor iron-oxide staining
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; pale gray-beige, dull to weakly granular luster, massive texture, and no obvious cleavage. Its smooth, rounded shape reflects stream or shoreline abrasion rather than crystal form.
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Physical properties
Hardness about 6.5–7 Mohs; pale gray-beige, dull to weakly granular luster, massive texture, and no obvious cleavage. Its smooth, rounded shape reflects stream or shoreline abrasion rather than crystal form.
Formation & geological history
Most likely a weathered cobble derived from quartzite or granite-rich rock, transported and rounded by flowing water; its exact geological age and source cannot be determined from the photograph.
Uses & applications
Usually valued as a natural curiosity, landscaping stone, or teaching specimen; quartzite can be used as aggregate and durable building stone, but this small cobble has no significant commercial use.
Geological facts
Quartz-rich rocks resist weathering, allowing them to survive transport while softer minerals wear away. The visible granular surface and pale color are consistent with quartz-rich material, though a hand specimen or test is needed for certainty.
Field identification & locations
Common in river gravels, glacial deposits, beaches, and weathered uplands. A glass-scratch test, lack of acid reaction, and visible interlocking quartz grains would support quartzite; softer, visibly crystalline feldspar-rich material would suggest granite.
