igneous
Granite
Granite; quartz–feldspar–mica plutonic rock
AI-generated identification · may be incorrectCoarse-grained, dark gray and cream, with interlocking quartz, feldspar, and dark biotite/hornblende; typically Mohs 6–7, vitreous to dull luster, no cleavage as a whole, and specific gravity about 2.6–2.7.
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Physical properties
Coarse-grained, dark gray and cream, with interlocking quartz, feldspar, and dark biotite/hornblende; typically Mohs 6–7, vitreous to dull luster, no cleavage as a whole, and specific gravity about 2.6–2.7.
Formation & geological history
Formed when silica-rich magma cooled slowly deep within continental crust, allowing visible crystals to grow; commonly Precambrian to Phanerozoic in age. The rounded shape indicates natural stream or glacial abrasion, or tumbling.
Uses & applications
Used extensively as dimension stone, countertops, monuments, aggregate, and decorative stone; attractive polished pieces are collected but usually modestly priced.
Geological facts
Granite is defined by abundant quartz and alkali feldspar, though this specimen may be a closely related granitic rock such as granodiorite.
Field identification & locations
Identify it by its speckled, interlocking crystals and lack of layering or foliation; a steel blade generally does not scratch quartz grains. Common worldwide in continental mountain belts, including India, Brazil, Canada, and the United States.
