igneous
Granite or granitic gneiss
Quartz–feldspar–mica granitoid; possibly foliated gneiss
AI-generated identification · may be incorrectCoarse, light gray-beige, speckled texture with visible dark biotite/hornblende; likely Mohs 6–7, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock. The elongated shape and surface weathering obscure its exact texture.
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Physical properties
Coarse, light gray-beige, speckled texture with visible dark biotite/hornblende; likely Mohs 6–7, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock. The elongated shape and surface weathering obscure its exact texture.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in Earth’s crust; related gneiss forms when granite is metamorphosed under high pressure and temperature. Such rocks commonly range from Precambrian to Mesozoic in age, depending on locality.
Uses & applications
Used as crushed aggregate, building stone, monuments, countertops, and landscaping material; attractive polished pieces may be collected but are usually low value.
Geological facts
Quartz appears glassy gray, feldspar is white or pink, and mica or amphibole forms black flakes. A streak test is generally unhelpful because the specimen is harder than the streak plate.
Field identification & locations
Common in continental mountain belts and exposed shields worldwide. Identify it by its coarse interlocking quartz-feldspar grains and black mafic minerals; visible layering or foliation would favor gneiss over granite.
