igneous
Likely weathered granite or granitic gneiss
Granite: quartz–feldspar–mica aggregate; possibly foliated gneiss
AI-generated identification · may be incorrectCoarse, uneven granular texture with gray quartz/feldspar and darker mica or amphibole; vitreous to dull luster, no obvious cleavage as a whole rock, and approximately Mohs 6–7. The specimen appears angular, weathered, and partly rusty from iron oxidation.
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Physical properties
Coarse, uneven granular texture with gray quartz/feldspar and darker mica or amphibole; vitreous to dull luster, no obvious cleavage as a whole rock, and approximately Mohs 6–7. The specimen appears angular, weathered, and partly rusty from iron oxidation.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust; gneiss forms when such rock is metamorphosed under high heat and pressure. Most examples are Precambrian to Phanerozoic, but the image alone cannot establish age.
Uses & applications
Used widely as crushed aggregate, dimension stone, paving, monuments, and countertops; attractive pieces may be collected but this fragment has little gem value.
Geological facts
The visible sparkling grains likely reflect quartz and mica, while brown coloration commonly indicates weathering of iron-bearing minerals.
Field identification & locations
Common in continental mountain belts and glacial or stream deposits. Identify it by interlocking visible grains, hardness, and lack of vesicles; a streak, acid, and close inspection of foliation would distinguish granite from gneiss and similar rocks.
