igneous
Granite
Coarse-grained felsic intrusive igneous rock, chiefly quartz, feldspar, and mica/amphibole
AI-generated identification · may be incorrectGray, granular, and moderately coarse-textured with a subdued vitreous-to-dull luster; typical hardness is about 6–7 Mohs, with no strong cleavage as a whole. The specimen appears weathered and may contain dark biotite or amphibole grains.
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Physical properties
Gray, granular, and moderately coarse-textured with a subdued vitreous-to-dull luster; typical hardness is about 6–7 Mohs, with no strong cleavage as a whole. The specimen appears weathered and may contain dark biotite or amphibole grains.
Formation & geological history
Granite forms when silica-rich magma cools slowly deep within continental crust, allowing large crystals to grow. Individual bodies range from Precambrian to Cenozoic age; the image alone cannot determine its age or exact variety.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving, aggregate, and building material; attractive varieties are polished for architectural use. Ordinary hand specimens have little commercial value.
Geological facts
Its visible interlocking crystals indicate slow underground cooling rather than volcanic eruption. Dark minerals commonly provide the black or greenish flecks seen in gray granite.
Field identification & locations
Identify it by its coarse interlocking grains, abundant light feldspar/quartz, and scattered dark mica or amphibole; it should not fizz with dilute acid. Common worldwide in continental mountain belts and exposed batholiths.
