igneous
Granite
Granite, chiefly quartz–feldspar–mica aggregate
AI-generated identification · may be incorrectCoarse-grained, speckled gray rock with interlocking crystals; likely quartz, plagioclase/alkali feldspar, and biotite or muscovite. Hardness about 6–7 Mohs, vitreous quartz luster, massive texture, no prominent cleavage as a whole, and specific gravity roughly 2.63–2.75.
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Physical properties
Coarse-grained, speckled gray rock with interlocking crystals; likely quartz, plagioclase/alkali feldspar, and biotite or muscovite. Hardness about 6–7 Mohs, vitreous quartz luster, massive texture, no prominent cleavage as a whole, and specific gravity roughly 2.63–2.75.
Formation & geological history
A plutonic igneous rock formed when silica-rich magma cooled slowly deep within continental crust, producing visible crystals; specimens may range from Precambrian to much younger Mesozoic or Cenozoic intrusions.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving, aggregate, and building cladding; ordinary hand specimens have little commercial value.
Geological facts
Its “salt-and-pepper” appearance reflects contrasting light feldspar/quartz and dark mica or amphibole. The exact rock could be granodiorite or tonalite if plagioclase predominates.
Field identification & locations
Identify it by coarse interlocking grains, abundant light feldspar/quartz, and scattered dark mica; it does not fizz with dilute hydrochloric acid and is much harder than marble. Common in continental mountain belts and granite quarries worldwide.
