igneous
Coarse-grained granite
Granitic plutonic rock, chiefly quartz, feldspar, and mica/amphibole
AI-generated identification · may be incorrectLight gray, speckled black-and-white, granular texture with visible interlocking crystals; likely Mohs hardness 6–7, vitreous quartz luster, and no preferred cleavage as a rock. Feldspars show cleavage, while quartz does not.
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Physical properties
Light gray, speckled black-and-white, granular texture with visible interlocking crystals; likely Mohs hardness 6–7, vitreous quartz luster, and no preferred cleavage as a rock. Feldspars show cleavage, while quartz does not.
Formation & geological history
Formed when silica-rich magma slowly cooled and crystallized deep within the continental crust, commonly during Precambrian to Phanerozoic intrusive events. The specimen may be weathered or glacially transported.
Uses & applications
Widely used as dimension stone, countertops, monuments, tiles, aggregate, and landscaping rock; ordinary hand specimens have little commercial value.
Geological facts
Its visible crystals indicate slow underground cooling rather than volcanic eruption. Dark grains are likely biotite or hornblende, and the white grains are feldspar.
Field identification & locations
Identify it by the coarse interlocking grains: translucent or gray quartz, white/pink feldspar, and black mica or amphibole. Common worldwide, especially in continental mountain belts and old shield regions; a streak test and acid test are usually unnecessary.
