igneous
Granite (likely biotite granite or granodiorite)
Coarse-grained granitoid; mainly quartz (SiO₂), feldspar, and biotite/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; mottled gray, pink, tan, and dark brown with a granular texture and mostly vitreous to dull luster. Interlocking crystals are visible; cleavage occurs in feldspar, while quartz has none. Typical specific gravity is 2.63–2.75.
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Physical properties
Hardness about 6–7 Mohs; mottled gray, pink, tan, and dark brown with a granular texture and mostly vitreous to dull luster. Interlocking crystals are visible; cleavage occurs in feldspar, while quartz has none. Typical specific gravity is 2.63–2.75.
Formation & geological history
Slow cooling of silica-rich magma deep within the continental crust, producing large crystals; most examples formed hundreds of millions to billions of years ago. Exact age cannot be determined from an image.
Uses & applications
Used extensively as building stone, countertops, monuments, aggregate, and paving; attractive polished pieces may be sold as inexpensive geological specimens.
Geological facts
The pink and pale grains are feldspar, translucent gray grains are quartz, and dark flakes are commonly biotite or amphibole. Granodiorite can look similar but generally contains more plagioclase than potassium feldspar.
Field identification & locations
Identify it by its coarse, interlocking mix of light quartz/feldspar and dark mica or amphibole; it is not layered and does not usually fizz with dilute acid. Common worldwide in continental mountain belts and exposed plutons.
