igneous
Granite
Granite; chiefly quartz (SiO₂), alkali feldspar and plagioclase, with minor biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, gray, speckled texture with vitreous quartz and feldspar; Mohs hardness ~6–7, nonfoliated, massive, with poor cleavage as a whole and specific gravity ~2.63–2.75.
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Physical properties
Coarse-grained, gray, speckled texture with vitreous quartz and feldspar; Mohs hardness ~6–7, nonfoliated, massive, with poor cleavage as a whole and specific gravity ~2.63–2.75.
Formation & geological history
A felsic intrusive igneous rock formed by slow cooling and crystallization of silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic mountain-building events.
Uses & applications
Widely used for countertops, monuments, floor and building stone, paving, aggregate, and architectural cladding; attractive polished varieties have decorative value.
Geological facts
The visible interlocking crystals indicate slow underground cooling. Gray granite can resemble granodiorite or gneiss; exact identification may require examining mineral proportions and texture.
Field identification & locations
Identify by its granular interlocking quartz–feldspar–mica texture, lack of layering, and inability to scratch with a steel knife. Common worldwide, including India, Brazil, Scandinavia, Canada, and the United States.
