igneous
Granite (likely biotite granite)
Coarse-grained plutonic rock composed chiefly of quartz, potassium feldspar, plagioclase, and biotite mica
AI-generated identification · may be incorrectHardness about 6–7 Mohs; speckled gray, white, pink, and black appearance with a granular texture, vitreous quartz luster, and no preferred cleavage as a whole. Visible interlocking crystals indicate slow cooling underground.
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Physical properties
Hardness about 6–7 Mohs; speckled gray, white, pink, and black appearance with a granular texture, vitreous quartz luster, and no preferred cleavage as a whole. Visible interlocking crystals indicate slow cooling underground.
Formation & geological history
Formed when silica-rich magma crystallized slowly in the crust, commonly during Precambrian to Phanerozoic plutonic events; exact age cannot be determined from the image.
Uses & applications
Widely used as building stone, countertops, monuments, paving, and aggregate; attractive hand specimens have modest collecting value.
Geological facts
Granite’s large crystals reflect prolonged cooling, often over thousands to millions of years. Dark flakes are commonly biotite or hornblende, while translucent grains are quartz.
Field identification & locations
Identify by its coarse interlocking grains and mixture of light quartz/feldspar with dark mica; it is common in continental mountain belts worldwide, including India, Brazil, Scandinavia, and North America. The right specimen could instead be a related granitic rock such as diorite.
