igneous
Granite
Granite (compositionally of Quartz, Alkali Feldspar, and Plagioclase)
Hardness: 6-7 on Mohs scale; Color: typically white, gray, or pink with dark specks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- typically white, gray, or pink with dark specks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: typically white, gray, or pink with dark specks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). It is predominantly of Phanerozoic age but can be found in ancient cratons over 3 billion years old.
Uses & applications
Widely used in construction, countertops, flooring, monuments, and as crushed stone for road base.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is extremely durable and iconic for being the rock used in Mount Rushmore.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. Common in mountain ranges and continental shield areas. Look for visible flakes of mica and glassy quartz.
