igneous
Weathered granite pebble
Granite; chiefly quartz, potassium feldspar, plagioclase, and minor biotite/hornblende
AI-generated identification · may be incorrectCoarse, speckled gray-tan appearance with visible interlocking grains; quartz has Mohs hardness 7, feldspar 6–6.5. Typically nonmetallic, dull to glassy, massive, and lacking cleavage as a whole; specific gravity about 2.63–2.75.
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Physical properties
Coarse, speckled gray-tan appearance with visible interlocking grains; quartz has Mohs hardness 7, feldspar 6–6.5. Typically nonmetallic, dull to glassy, massive, and lacking cleavage as a whole; specific gravity about 2.63–2.75.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic plutonic events; this rounded specimen was likely shaped by stream or glacial abrasion and weathering.
Uses & applications
Used extensively as dimension stone, countertops, monuments, building aggregate, and landscaping rock; ordinary pebbles have negligible commercial value.
Geological facts
The light grains are feldspar and quartz, while darker flecks are commonly biotite or amphibole. Its granular texture records slow underground cooling.
Field identification & locations
Identify it by visible interlocking light and dark crystals, lack of layering, and inability to scratch quartz with a steel knife; vinegar produces no reaction. Common worldwide, especially in continental mountain belts and glacial deposits.
