igneous
Weathered granite or granitic gneiss
Granite; predominantly quartz, feldspar, and mica (exact identification is uncertain from the image)
AI-generated identification · may be incorrectCoarse-grained, speckled gray-brown rock with visible pale feldspar/quartz and darker mica or amphibole; typically Mohs hardness 6–7, nonmetallic luster, interlocking crystals, and no obvious cleavage as a whole rock.
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Physical properties
Coarse-grained, speckled gray-brown rock with visible pale feldspar/quartz and darker mica or amphibole; typically Mohs hardness 6–7, nonmetallic luster, interlocking crystals, and no obvious cleavage as a whole rock.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic continental mountain-building; surface weathering has rounded and oxidized this specimen.
Uses & applications
Used extensively as dimension stone, countertops, monuments, aggregate, and decorative material; attractive specimens have modest collector value.
Geological facts
The granular texture reflects slow underground cooling, while rusty colors generally indicate oxidation of iron-bearing minerals.
Field identification & locations
Identify it by its coarse interlocking texture, quartz-feldspar-mica mix, and inability to scratch quartz; common worldwide in continental shields and mountain belts. A field test with dilute acid should show little or no reaction.
