igneous
Granite
Phaneritic plutonic rock (dominated by SiO2, Al2O3, K2O, Na2O)
Hardness: 6-7 on Mohs scale; Color: typically mottled pink, white, gray, and black; Luster: vitreous to dull; Crystal structure: phaneritic (coarsegrained) with visible crystals of quartz, feldspar, and mica; Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- typically mottled pink, white, gray, and black
- Luster
- vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: typically mottled pink, white, gray, and black; Luster: vitreous to dull; Crystal structure: phaneritic (coarsegrained) with visible crystals of quartz, feldspar, and mica; Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow crystallization of silica-rich magma beneath the Earth's surface. Most granite dates back to the Precambrian or Paleozoic eras, forming at depths of several kilometers under high pressure and temperature.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Also used as crushed stone (aggregate) for road base and concrete.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota. It is one of the hardest and most durable natural stones used by humans.
Field identification & locations
Identify by its 'salt and pepper' appearance and large, interlocking visible crystals. Look for translucent quartz grains and blocky, opaque feldspar. Found globally in continental mountain ranges and shield areas like the Canadian Shield or the Appalachians.
