igneous
Granite
Granite; primarily quartz, feldspar, and mica (commonly biotite)
AI-generated identification · may be incorrectCoarse-grained, speckled gray-brown rock with interlocking crystals; quartz and feldspar provide Mohs hardness ~6–7, mica ~2–3. It has a vitreous-to-pearly luster, no consistent cleavage as a whole, and specific gravity around 2.63–2.75.
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Physical properties
Coarse-grained, speckled gray-brown rock with interlocking crystals; quartz and feldspar provide Mohs hardness ~6–7, mica ~2–3. It has a vitreous-to-pearly luster, no consistent cleavage as a whole, and specific gravity around 2.63–2.75.
Formation & geological history
Intrusive igneous rock formed when silica-rich magma cooled slowly deep within continental crust, allowing large crystals to grow. Most granite is Precambrian to Phanerozoic in age, depending on locality.
Uses & applications
Widely used as dimension stone, countertops, monuments, building façades, paving, and aggregate; attractive hand specimens are inexpensive collector pieces.
Geological facts
The visible light and dark grains reflect contrasting feldspar/quartz and mafic minerals. Weathering commonly rounds granite into boulders and may produce sandy grus.
Field identification & locations
Identify it by its coarse, interlocking texture and visible quartz, feldspar, and mica; unlike gneiss, it lacks strong mineral banding. Common worldwide in continental mountain belts and exposed plutons.
