igneous
Weathered granite or granitic gneiss
Granite: quartz–feldspar–mica rock; possibly altered granitic gneiss
AI-generated identification · may be incorrectCoarse, granular texture with pale quartz/feldspar, dark mica or amphibole, and green surface staining likely from chlorite or epidote. Typical hardness is about 6–7 Mohs, vitreous to dull luster, interlocking crystals, and no prominent cleavage as a whole rock.
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Physical properties
Coarse, granular texture with pale quartz/feldspar, dark mica or amphibole, and green surface staining likely from chlorite or epidote. Typical hardness is about 6–7 Mohs, vitreous to dull luster, interlocking crystals, and no prominent cleavage as a whole rock.
Formation & geological history
Formed from slowly cooled silica-rich magma deep in the continental crust, generally Precambrian to Paleozoic in age; the rough exterior reflects weathering and oxidation. If gneissic, it also experienced later high-grade metamorphism.
Uses & applications
Commonly used as crushed aggregate, dimension stone, monuments, countertops, and landscaping rock; this irregular specimen has modest collector value.
Geological facts
Granite is identified by visible quartz and feldspar grains, commonly with black biotite. Green patches may indicate secondary alteration rather than the primary rock composition.
Field identification & locations
Look for interlocking light and dark mineral grains, hardness sufficient to scratch glass, and lack of fizzing with dilute acid; a fresh broken surface would improve identification. Common worldwide, especially in continental shields and mountain belts.
