igneous
Granite
Coarse-grained felsic intrusive igneous rock; chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; speckled white, gray, black, and tan appearance with a granular texture and mostly vitreous-to-dull luster. Interlocking crystals are visible, with no obvious cleavage as a whole rock; specific gravity typically 2.63–2.75.
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Physical properties
Hardness about 6–7 Mohs; speckled white, gray, black, and tan appearance with a granular texture and mostly vitreous-to-dull luster. Interlocking crystals are visible, with no obvious cleavage as a whole rock; specific gravity typically 2.63–2.75.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep within the continental crust, commonly during Precambrian to Phanerozoic mountain-building events. The specimen may also be granodiorite, which has relatively more plagioclase than true granite.
Uses & applications
Widely used as dimension stone, countertops, monuments, building cladding, paving, and aggregate; attractive polished pieces are used decoratively but are not typically gemstones.
Geological facts
Its visible coarse crystals indicate intrusive cooling rather than volcanic eruption. Dark minerals commonly represent biotite or amphibole, while pale grains are feldspar and quartz.
Field identification & locations
Identify it by its hard, interlocking, multicolored crystals and resistance to scratching; quartz usually appears gray and glassy, while feldspar is blocky and pale. Common worldwide in continental batholiths and ancient shield regions.
