igneous
Granite
Phaneritic plutonic rock (SiO2 range 65-75%)
Hardness: 6-7 Mohs; Color: Salt and pepper/mottled grey, white, and black; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Cleavage: None (minerals within have individual cleavage); Specific Gravity: 2.6-2.7.
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper/mottled grey, white, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper/mottled grey, white, and black; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Cleavage: None (minerals within have individual cleavage); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed from the slow crystallization of silica-rich magma deep beneath the Earth's surface (plutonic) within the continental crust over millions of years.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Highly valued in the dimension stone industry for its durability.
Geological facts
Granite is one of the most common rocks in the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. It will not be scratched by a steel pocket knife.
