igneous
Weathered granite or granitic gneiss
Quartz–feldspar–mica granitoid; possibly weakly gneissic
AI-generated identification · may be incorrectCoarse, speckled gray-brown rock with visible pale feldspar/quartz and dark biotite or iron-oxide staining; likely Mohs 6–7, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock.
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Physical properties
Coarse, speckled gray-brown rock with visible pale feldspar/quartz and dark biotite or iron-oxide staining; likely Mohs 6–7, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock.
Formation & geological history
Formed from slowly cooled silica-rich magma deep in the crust, commonly Precambrian to Phanerozoic in age; surface weathering has produced the brown coloration and softened edges.
Uses & applications
Used as crushed aggregate, road stone, building stone, landscaping rock, and monuments; this ordinary hand specimen has little commercial gemstone value.
Geological facts
Granite is identified by visible quartz, feldspar, and mica crystals; gneiss shows compositional banding, which is not clearly visible here.
Field identification & locations
Common worldwide, especially in continental shields and mountain belts. A fresh broken surface should reveal gray quartz, white/pink feldspar, and black mica; dilute acid should not visibly fizz.
