igneous
Granite pebble
Granite; chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, mottled gray, pink, black, and tan; generally Mohs 6–7, vitreous quartz, feldspar luster, no preferred cleavage as a whole, and specific gravity about 2.63–2.75.
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Physical properties
Coarse-grained, mottled gray, pink, black, and tan; generally Mohs 6–7, vitreous quartz, feldspar luster, no preferred cleavage as a whole, and specific gravity about 2.63–2.75.
Formation & geological history
An intrusive felsic igneous rock crystallized slowly from silica-rich magma deep in the crust, typically during Precambrian to Phanerozoic mountain-building; this rounded specimen was likely shaped by stream or wave abrasion.
Uses & applications
Used as crushed aggregate, dimension stone, paving, monuments, countertops, and landscaping material; ordinary pebbles have little commercial value.
Geological facts
Its visible interlocking crystals distinguish granite from fine-grained volcanic rhyolite; pink areas are potassium feldspar, gray translucent grains are quartz, and black grains are mafic minerals.
Field identification & locations
Identify it by its visibly interlocking, multicolored grains and lack of layering or foliation; common worldwide, especially in continental shields and mountain belts. A glassy streak or acid reaction would suggest a different material.
