igneous
Weathered granite or granitic gneiss
Granite; chiefly quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, tan to gray rock with visible pale feldspar, darker mafic minerals, and possible quartz; hardness about 6–7 Mohs, generally nonmetallic luster, interlocking crystals, and poor or absent cleavage as a whole. The image is low-resolution, so exact identification is uncertain.
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Physical properties
Coarse-grained, tan to gray rock with visible pale feldspar, darker mafic minerals, and possible quartz; hardness about 6–7 Mohs, generally nonmetallic luster, interlocking crystals, and poor or absent cleavage as a whole. The image is low-resolution, so exact identification is uncertain.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust; associated gneiss may form when granite is metamorphosed. Most exposed examples are Precambrian to Phanerozoic, depending on locality.
Uses & applications
Used widely as crushed aggregate, road stone, building stone, monuments, countertops, and landscaping material; attractive polished pieces are collectible but usually modestly valuable.
Geological facts
The specimen appears rounded and weathered, suggesting transport in gravel or river sediment. Dark spots likely represent biotite or amphibole, while tan areas are weathered feldspar.
Field identification & locations
Look for visible interlocking crystals and a speckled quartz–feldspar–dark-mineral texture; granite lacks the layering typical of sedimentary rocks. Common worldwide, especially in continental mountain belts.
