igneous
Rounded granite cobble
Granite, a coarse-grained felsic intrusive igneous rock
AI-generated identification · may be incorrectVisible interlocking grains of pale quartz and feldspar with dark biotite or amphibole; typically Mohs 6–7, granular texture, no cleavage at the rock scale, and specific gravity about 2.6–2.7. The rounded shape and smooth surface likely result from water or sediment abrasion.
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Physical properties
Visible interlocking grains of pale quartz and feldspar with dark biotite or amphibole; typically Mohs 6–7, granular texture, no cleavage at the rock scale, and specific gravity about 2.6–2.7. The rounded shape and smooth surface likely result from water or sediment abrasion.
Formation & geological history
Formed by slow cooling and crystallization of silica-rich magma underground; its precise age and source cannot be determined from the image. Later weathering and transport rounded the cobble.
Uses & applications
Granite is widely used for building stone, paving, countertops, and aggregate; this small cobble is mainly suitable for collecting or landscaping.
Geological facts
Granite commonly contains quartz, alkali feldspar, plagioclase, and minor dark minerals. Its contrasting mineral grains make it recognizable even after natural rounding.
Field identification & locations
Look for a speckled, interlocking mixture of light quartz/feldspar and darker minerals; unlike sandstone, it has no layered or cemented grains. Granite occurs worldwide, especially in continental crust and glacial or river deposits.
