igneous
Granite
Granite, chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, speckled gray-white rock with black mica or amphibole; vitreous quartz and feldspar luster, no foliation, Mohs hardness about 6–7, and poor cleavage as a whole.
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Physical properties
Coarse-grained, speckled gray-white rock with black mica or amphibole; vitreous quartz and feldspar luster, no foliation, Mohs hardness about 6–7, and poor cleavage as a whole.
Formation & geological history
An intrusive felsic igneous rock crystallized slowly from silica-rich magma deep in the continental crust, commonly during Precambrian to Phanerozoic mountain-building events.
Uses & applications
Widely used for countertops, monuments, building stone, paving, aggregate, and decorative specimens; this rough piece has little jewelry value.
Geological facts
Visible interlocking crystals indicate slow underground cooling. The image may also represent a closely related granodiorite, which contains more plagioclase than true granite.
Field identification & locations
Identify it by its coarse interlocking crystals, pink or white feldspar, gray translucent quartz, and scattered black minerals; it does not fizz with dilute acid. Common worldwide, especially in continental shields and mountain belts.
