igneous
Weathered granite or granitic gneiss
Granite; primarily quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, gray-tan rock with visible quartz/feldspar and dark mica or mafic minerals; hardness about 6–7 Mohs, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock.
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Physical properties
Coarse-grained, gray-tan rock with visible quartz/feldspar and dark mica or mafic minerals; hardness about 6–7 Mohs, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock.
Formation & geological history
Likely formed when silica-rich magma slowly crystallized deep underground, generally in Precambrian to younger continental crust; surface weathering rounded and stained the specimen.
Uses & applications
Used as crushed aggregate, dimension stone, paving, monuments, and landscaping; this weathered piece is mainly of educational or decorative interest.
Geological facts
Granite commonly develops rounded ‘corestones’ through spheroidal weathering. The image does not show enough detail to distinguish true granite from strongly foliated granitic gneiss with certainty.
Field identification & locations
Look for interlocking light quartz/feldspar grains and scattered dark mica; a streak test is usually white, and dilute acid produces no fizz unless carbonate contamination is present. Common worldwide, especially in continental mountain belts and shield regions.
