igneous
Granite
Granite; primarily quartz (SiO₂), alkali feldspar, plagioclase, and mica
AI-generated identification · may be incorrectCoarse-grained, speckled gray-white rock with black mica/amphibole; vitreous quartz, feldspar cleavage, Mohs hardness about 6–7, and specific gravity roughly 2.6–2.7. The visible specimen appears weathered or naturally fractured.
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Physical properties
Coarse-grained, speckled gray-white rock with black mica/amphibole; vitreous quartz, feldspar cleavage, Mohs hardness about 6–7, and specific gravity roughly 2.6–2.7. The visible specimen appears weathered or naturally fractured.
Formation & geological history
An intrusive igneous rock formed when silica-rich magma cooled slowly deep within continental crust, allowing large crystals to grow. Most granite formed during Precambrian to Phanerozoic plutonic events, commonly hundreds of millions to billions of years ago.
Uses & applications
Widely used as dimension stone, countertops, monuments, paving, aggregate, and decorative objects; attractive hand specimens have modest collector value.
Geological facts
Its interlocking crystals distinguish it from volcanic rhyolite, which is usually fine-grained. Black minerals are commonly biotite or hornblende, while the glassy grains are quartz.
Field identification & locations
Identify it by visible interlocking white/pink feldspar, gray translucent quartz, and black mica or amphibole; it does not fizz with dilute hydrochloric acid. Common worldwide in continental mountain belts and exposed plutons.
