igneous
Weathered granite or granitic gneiss
Granite; chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, pink-orange and gray, with a granular texture and vitreous-to-dull luster; quartz has Mohs hardness 7, feldspars 6–6.5, and overall specific gravity about 2.6–2.7. The image is insufficient to distinguish massive granite from weakly foliated granitic gneiss.
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Physical properties
Coarse-grained, pink-orange and gray, with a granular texture and vitreous-to-dull luster; quartz has Mohs hardness 7, feldspars 6–6.5, and overall specific gravity about 2.6–2.7. The image is insufficient to distinguish massive granite from weakly foliated granitic gneiss.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, generally during Precambrian to Phanerozoic plutonic events; gneiss forms when such rock is metamorphosed under high temperature and pressure. Weathering has exposed and rounded the specimen.
Uses & applications
Crushed granite is used for aggregate, road stone, and building material; intact blocks are used for countertops and monuments. Ordinary hand specimens have little commercial value.
Geological facts
The pink color commonly comes from potassium feldspar, while dark flakes are biotite or hornblende and translucent grains are quartz. Granite is a major component of continental crust.
Field identification & locations
Identify it by visible interlocking pink feldspar, gray/clear quartz, and dark mica or amphibole; it should not fizz with dilute hydrochloric acid. Common in continental shields, mountain belts, and quarry areas worldwide.
