igneous
Coarse-grained granite
Granite, composed mainly of quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pink, gray, white, and black granular crystals with a dull to vitreous luster. Massive, interlocking crystalline texture and no obvious cleavage as a whole; density typically 2.6–2.8 g/cm³.
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Physical properties
Hardness about 6–7 Mohs; pink, gray, white, and black granular crystals with a dull to vitreous luster. Massive, interlocking crystalline texture and no obvious cleavage as a whole; density typically 2.6–2.8 g/cm³.
Formation & geological history
An intrusive igneous rock formed by slow cooling and crystallization of silica-rich magma deep in continental crust. Individual specimens may range from Precambrian to younger geologic ages, depending on source locality.
Uses & applications
Widely used as building stone, countertops, monuments, paving, aggregate, and decorative facing. Ordinary hand specimens have modest collector value.
Geological facts
The visible speckled texture reflects crystals large enough to see without magnification, indicating slow underground cooling. Pink areas are potassium feldspar, gray translucent grains are quartz, and dark grains are commonly biotite or amphibole.
Field identification & locations
Identify it by its interlocking pink/white/gray/black grains, lack of layering, and inability to scratch easily with a steel knife; quartz may scratch glass. Common worldwide in continental mountain belts and exposed batholiths.
