igneous
Weathered granitic rock (probable granite or granodiorite)
Granite–granodiorite; chiefly quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectTypically Mohs 6–7, coarse-grained, gray to pink with black mica or amphibole, and a vitreous-to-dull luster. Interlocking crystals show no obvious cleavage as a whole, though feldspar and mica cleave; the specimen appears strongly weathered and iron-stained.
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Physical properties
Typically Mohs 6–7, coarse-grained, gray to pink with black mica or amphibole, and a vitreous-to-dull luster. Interlocking crystals show no obvious cleavage as a whole, though feldspar and mica cleave; the specimen appears strongly weathered and iron-stained.
Formation & geological history
Slow cooling of silica-rich magma deep in the crust produced its intrusive texture, usually during Precambrian to Phanerozoic mountain-building. Surface exposure caused oxidation, staining, and granular breakdown.
Uses & applications
Used widely as crushed aggregate, dimension stone, countertops, monuments, and building cladding; this weathered piece has little commercial or jewelry value.
Geological facts
Granite is defined by abundant quartz and alkali feldspar, whereas granodiorite contains more plagioclase. Exact identification requires a fresh broken surface or thin-section examination.
Field identification & locations
Look for visible interlocking quartz, white/pink feldspar, and dark mica or hornblende; a steel file generally scratches little or not at all. Common worldwide in continental shields, mountain belts, and exposed plutons.
