igneous
Weathered granitic rock (likely granite or granodiorite)
Granite–granodiorite; quartz + feldspar + dark mica/amphibole
AI-generated identification · may be incorrectCoarse crystalline, tan-gray and mottled, with dull to weakly glassy luster and irregular fractures; typical hardness is about 6–7 Mohs and specific gravity 2.6–2.8. The image is slightly out of focus, so exact mineral identification is uncertain.
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Physical properties
Coarse crystalline, tan-gray and mottled, with dull to weakly glassy luster and irregular fractures; typical hardness is about 6–7 Mohs and specific gravity 2.6–2.8. The image is slightly out of focus, so exact mineral identification is uncertain.
Formation & geological history
Slow cooling of silica-rich magma deep in Earth’s crust produced interlocking crystals, generally during Precambrian to Phanerozoic continental plutonism; surface weathering rounded and altered the specimen.
Uses & applications
Common granite is used for building stone, countertops, monuments, aggregate, and landscaping; ordinary hand specimens have little commercial value.
Geological facts
Quartz is commonly translucent gray, feldspar is white/tan, and biotite or hornblende creates dark streaks. It is distinguished from basalt by its lighter color and visible coarse grains.
Field identification & locations
Common worldwide in continental mountain belts and exposed plutons; inspect a fresh surface for visible quartz and feldspar, and use a steel knife or glass scratch test cautiously. Exact naming requires a fresh break or microscopy.
