igneous
Granite or granitic gneiss cobble
Quartz–feldspar–mica aggregate; possibly weathered gneiss
AI-generated identification · may be incorrectLight gray, coarse-grained, with visible pale feldspar, translucent quartz, and dark mica; typically Mohs 6–7, nonmetallic luster, interlocking crystals, and no cleavage as a whole rock. The image is partly obscured, so exact identification is limited.
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Physical properties
Light gray, coarse-grained, with visible pale feldspar, translucent quartz, and dark mica; typically Mohs 6–7, nonmetallic luster, interlocking crystals, and no cleavage as a whole rock. The image is partly obscured, so exact identification is limited.
Formation & geological history
Likely an eroded glacial or stream-rounded fragment of continental crust; granite crystallizes slowly from magma, while gneiss forms by high-grade metamorphism. Such rocks commonly range from Precambrian to younger Phanerozoic ages.
Uses & applications
Used as crushed aggregate, road stone, building stone, curbing, countertops, monuments, and landscaping material; this weathered cobble has little commercial value.
Geological facts
Granite’s visible crystals indicate slow cooling deep underground; gneiss may show compositional banding, though no clear banding is visible here.
Field identification & locations
Look for interlocking quartz, feldspar, and mica grains; granite is generally massive, whereas gneiss displays foliation or banding. Common in glacial deposits, mountain regions, stream gravels, and continental shields.
