igneous
Weathered granite or granitic gneiss fragment
Granite; chiefly quartz (SiO₂), feldspar, and mica
AI-generated identification · may be incorrectMedium-grained, tan-gray, granular texture with visible dark mica and pale feldspar; vitreous to dull luster, no obvious cleavage as a whole, Mohs hardness about 6–7, specific gravity roughly 2.6–2.7. The image is insufficient to distinguish granite from weakly foliated gneiss confidently.
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Physical properties
Medium-grained, tan-gray, granular texture with visible dark mica and pale feldspar; vitreous to dull luster, no obvious cleavage as a whole, Mohs hardness about 6–7, specific gravity roughly 2.6–2.7. The image is insufficient to distinguish granite from weakly foliated gneiss confidently.
Formation & geological history
Crystallized slowly from silica-rich magma deep underground, typically during Precambrian to Phanerozoic mountain-building; surface weathering produced the rounded, rough fragment.
Uses & applications
Commonly used as crushed aggregate, building stone, paving, monuments, and landscaping material; this fragment has little commercial value unless it has unusual provenance or attractive texture.
Geological facts
Quartz resists weathering while feldspar alters to clay, producing the rough, granular surface. Dark streaks may be biotite mica or minor amphibole.
Field identification & locations
Identify it by interlocking visible grains, abundant light feldspar/quartz, and scattered dark mica; a glassy fracture and lack of vesicles help distinguish it from volcanic rock. Common worldwide in continental crust and glacial tills.
