igneous
Granite (rounded cobble)
Felsic intrusive igneous rock; chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectTypically Mohs 6–7, coarse crystalline, gray to pink or white, with a granular texture and vitreous quartz; lacks strong cleavage as a whole, though feldspars have cleavage. The specimen appears weathered and water-rounded.
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Physical properties
Typically Mohs 6–7, coarse crystalline, gray to pink or white, with a granular texture and vitreous quartz; lacks strong cleavage as a whole, though feldspars have cleavage. The specimen appears weathered and water-rounded.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the continental crust, generally during Precambrian to Phanerozoic intrusive events; later exposed and rounded by erosion or transport.
Uses & applications
Widely used as dimension stone, monuments, countertops, paving, aggregate, and landscaping rock; attractive pieces are collected but are usually low-value.
Geological facts
Granite’s visible interlocking crystals record slow underground cooling. Its gray appearance commonly reflects abundant quartz and plagioclase with lesser dark mica or amphibole.
Field identification & locations
Identify by its coarse, interlocking quartz–feldspar texture and hardness; unlike many gneisses, it lacks persistent foliation or banding. Common worldwide, especially in continental shields and mountain belts.
