igneous
Granite
Granite (composed primarily of Quartz SiO2, Feldspar (KAlSi3O8), and Mica)
Hardness: 6-7 on Mohs scale; Color: Gray, white, pink, or speckled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (though constituent minerals like mica have perfect cleavage); Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Gray, white, pink, or speckled
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Gray, white, pink, or speckled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (though constituent minerals like mica have perfect cleavage); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). Most granites date from the Precambrian to Cenozoic eras, typically found in continental crust and mountain ranges.
Uses & applications
Used extensively in construction for countertops, floor tiles, paving stones, curbing, and monuments. It is also a popular specimen for educational geology kits.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith, and Yosemite’s Half Dome is a famous granite monolith.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz and feldspar. Found globally in mountainous regions or areas where ancient rock is exposed. Use a hand lens to see the glassy quartz and opaque feldspar blocks.
