igneous
Granite (weathered, rounded cobble)
Felsic intrusive igneous rock; chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, mottled pink-gray, white, and black appearance with a granular texture and dull to weakly vitreous luster. Quartz hardness is 7 Mohs; feldspars are about 6, with no dominant cleavage in the whole rock and typical specific gravity of 2.63–2.75.
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Physical properties
Coarse-grained, mottled pink-gray, white, and black appearance with a granular texture and dull to weakly vitreous luster. Quartz hardness is 7 Mohs; feldspars are about 6, with no dominant cleavage in the whole rock and typical specific gravity of 2.63–2.75.
Formation & geological history
Formed when silica-rich magma slowly crystallized deep within continental crust, commonly hundreds of millions to billions of years ago; surface weathering and stream transport rounded this specimen.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving, aggregate, and building stone; attractive polished pieces are also collected.
Geological facts
The visible dark patches are likely biotite or amphibole, while pale pink areas are potassium feldspar and translucent grains are quartz.
Field identification & locations
Identify it by interlocking visible crystals, quartz-rich gray or pink coloration, and inability to scratch quartz with a steel knife. Common worldwide, especially in continental shields and mountain batholiths.
