igneous
Weathered granite pebble
Granite, predominantly quartz–feldspar–mica aggregate
AI-generated identification · may be incorrectLight gray to yellowish, coarse-grained, speckled black and white, with a dull weathered luster and no obvious cleavage as a whole rock. Typical hardness is about 6–7 Mohs; composition commonly includes quartz, plagioclase and potassium feldspar, with biotite or hornblende.
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Physical properties
Light gray to yellowish, coarse-grained, speckled black and white, with a dull weathered luster and no obvious cleavage as a whole rock. Typical hardness is about 6–7 Mohs; composition commonly includes quartz, plagioclase and potassium feldspar, with biotite or hornblende.
Formation & geological history
Intrusive igneous rock crystallized slowly from silica-rich magma deep within Earth, commonly during Precambrian to Phanerozoic mountain-building events. The rounded shape and altered surface indicate transport and weathering, but the exact age cannot be determined visually.
Uses & applications
Used widely as crushed aggregate, building stone, paving material, monuments and countertops; attractive polished pieces are collected but are generally low value.
Geological facts
Granite’s visible crystals formed because magma cooled slowly underground. Dark flecks are likely biotite or hornblende, while pale grains are feldspar and quartz.
Field identification & locations
Identify it by its interlocking visible crystals, hard granular texture and mixed light/dark minerals; a steel scratch test should usually fail or leave only a faint mark. Common worldwide, especially in exposed mountain belts and glacial or river gravels.
