igneous
Weathered granite or granitic gneiss
Granite; primarily quartz, potassium feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse, granular, pale gray-tan rock with visible interlocking quartz and feldspar grains plus dark mica/amphibole; typically Mohs 6–7, vitreous quartz luster, and no prominent cleavage as a whole. The rounded surface indicates strong weathering and abrasion.
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Physical properties
Coarse, granular, pale gray-tan rock with visible interlocking quartz and feldspar grains plus dark mica/amphibole; typically Mohs 6–7, vitreous quartz luster, and no prominent cleavage as a whole. The rounded surface indicates strong weathering and abrasion.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the continental crust, generally during Precambrian to Phanerozoic intrusive events; weathering and transport rounded this specimen. If foliation is present, it may instead be granitic gneiss, a metamorphosed equivalent.
Uses & applications
Crushed granite is used for aggregate, road base, concrete, and ballast; sound blocks are used for monuments, countertops, and building stone. Unusual textures may have modest lapidary or educational value.
Geological facts
Quartz appears glassy gray, feldspar is cream or pink and blocky, and dark minerals are mica or amphibole. Granite commonly develops rounded corestones through spheroidal weathering.
Field identification & locations
Common in continental mountain belts and exposed plutons worldwide. A fresh broken surface, acid test, and hand lens help distinguish it from sandstone or weathered concrete; field identification is provisional from the photo.
