igneous
Weathered granitic rock (likely granite or granodiorite)
Granite–granodiorite; mainly quartz, feldspar, and dark mica/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; coarse, speckled gray, tan, and black grains with a dull to slightly granular luster. Interlocking crystals are visible, but weathering obscures the texture; cleavage occurs in feldspar, not the whole rock.
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Physical properties
Hardness about 6–7 Mohs; coarse, speckled gray, tan, and black grains with a dull to slightly granular luster. Interlocking crystals are visible, but weathering obscures the texture; cleavage occurs in feldspar, not the whole rock.
Formation & geological history
An intrusive igneous rock that crystallized slowly from magma deep underground, commonly during Precambrian to younger continental crust formation. Surface weathering rounded and stained this specimen.
Uses & applications
Used as crushed aggregate, dimension stone, countertops, monuments, and landscaping rock; this small weathered piece has little jewelry value.
Geological facts
Granite is defined by abundant quartz and alkali feldspar, while granodiorite contains more plagioclase. Iron-bearing minerals commonly produce the rusty brown surface coating.
Field identification & locations
Likely from continental or mountainous terrain; identify by its visible interlocking quartz/feldspar grains, hardness, and lack of layering or fossils. A definitive identification requires a fresh break or thin section.
