igneous
Rounded granite cobble
Granite, a coarse-grained felsic intrusive igneous rock composed chiefly of quartz, feldspar, and mica
AI-generated identification · may be incorrectPale tan-gray, speckled, and granular, with a dull to slightly glassy luster; typically Mohs 6–7 and made of interlocking crystals. The rounded shape and smooth surface appear to result from natural abrasion or weathering.
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Physical properties
Pale tan-gray, speckled, and granular, with a dull to slightly glassy luster; typically Mohs 6–7 and made of interlocking crystals. The rounded shape and smooth surface appear to result from natural abrasion or weathering.
Formation & geological history
Granite forms as silica-rich magma cools slowly deep in Earth’s crust. Granite bodies occur across many geological ages; the cobble’s age and precise source cannot be determined from the photo.
Uses & applications
Granite is widely used for building stone, paving, countertops, and monuments; cobbles may be used in landscaping or collected as natural specimens.
Geological facts
Its visible grains are intergrown minerals rather than separate pebbles. The specimen’s rounded outline is not its original igneous form.
Field identification & locations
Look for a speckled mix of light feldspar and quartz with darker mica or amphibole grains, and a hard, crystalline texture. Granite is common in continental crust and glacial or river deposits; a loose cobble’s location of origin is uncertain.
