igneous
Granite
Coarse-grained felsic intrusive igneous rock, mainly quartz, alkali feldspar, plagioclase, and mica
AI-generated identification · may be incorrectTypically medium- to coarse-grained, mottled pink, white, gray, and black; vitreous quartz and pearly feldspar with black biotite. Hardness is about 6–7 Mohs; crystals are interlocking and lack cleavage as a whole, though feldspars cleave.
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Physical properties
Typically medium- to coarse-grained, mottled pink, white, gray, and black; vitreous quartz and pearly feldspar with black biotite. Hardness is about 6–7 Mohs; crystals are interlocking and lack cleavage as a whole, though feldspars cleave.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic plutonic events. The specimen appears sawn or broken from a larger block.
Uses & applications
Widely used for countertops, monuments, building stone, paving, and aggregate; attractive pieces are collected as geological specimens. It is generally low-value commercially.
Geological facts
Pink coloration commonly comes from potassium feldspar, while black flakes are biotite or hornblende. Its coarse texture records slow underground cooling.
Field identification & locations
Identify by visible interlocking crystals of quartz, feldspar, and dark mica; unlike rhyolite, crystals are readily visible, and unlike gneiss, it lacks strong compositional banding. Common worldwide in continental mountain belts and exposed plutons.
