igneous
Weathered granite or granitic gneiss
Felsic plutonic rock, primarily quartz, feldspar, and mica; possible gneissic deformation
AI-generated identification · may be incorrectCoarse-grained, speckled gray-white-brown texture with quartz and feldspar; glassy quartz luster, hard (Mohs 6–7), massive to weakly foliated, with no obvious cleavage as a whole rock.
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Physical properties
Coarse-grained, speckled gray-white-brown texture with quartz and feldspar; glassy quartz luster, hard (Mohs 6–7), massive to weakly foliated, with no obvious cleavage as a whole rock.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the crust, generally Precambrian to Phanerozoic in age; surface weathering has produced the brown exterior. If foliation is confirmed, it was later metamorphosed into gneiss.
Uses & applications
Commonly used as crushed stone, aggregate, building stone, monuments, countertops, and landscape rock; this irregular specimen has little jewelry value.
Geological facts
Granite commonly contains interlocking crystals large enough to see without magnification. Brown staining is typically iron-oxide weathering along fractures and feldspar surfaces.
Field identification & locations
Look for visible interlocking quartz, white or pink feldspar, and dark mica; a streak test is usually white, and dilute acid should not fizz. Common worldwide, especially in continental shields and mountain belts.
