igneous
Granite-like glacial cobble
Likely granitoid, chiefly quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, gray, granular texture with dark mineral flecks; likely Mohs 6–7, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock. Exact identification is limited by the photograph.
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Physical properties
Coarse-grained, gray, granular texture with dark mineral flecks; likely Mohs 6–7, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock. Exact identification is limited by the photograph.
Formation & geological history
Formed by slow cooling of silica-rich magma, probably hundreds of millions to billions of years ago; later exposed and rounded by weathering, stream transport, or glacial abrasion.
Uses & applications
Commonly used as aggregate, paving stone, building stone, and landscaping material; this rounded specimen has little commercial or collector value.
Geological facts
The rounded shape and weathered surface suggest a transported cobble rather than an in-place bedrock fragment. A fresh broken surface would reveal the mineral grains more clearly.
Field identification & locations
Look for visible quartz grains, pale pink/white feldspar, and black mica or amphibole; a knife should not scratch the grains easily, while vinegar should produce no reaction. Common in glacial deposits, river gravels, and granite-bearing regions.
