igneous
Granite
Phaneritic Plutonic Felsic Rock (SiO2, KAlSi3O8, NaAlSi3O8, CaAl2Si2O8)
Hardness: 6-7 on Mohs scale; Color: Salt and pepper/mottled white, grey, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.65-2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper/mottled white, grey, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper/mottled white, grey, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.65-2.75.
Formation & geological history
Formed by the slow crystallization of magma below the Earth's surface in continental crust. These intrusive plutons can range from billions of years old to relatively young in geological terms.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, monuments, and as crushed stone for road base.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Because it is so hard and dense, it can be polished to a mirror finish, a property valued in architecture.
Field identification & locations
Identify in the field by looking for a coarse-grained, interlocking texture of light-colored minerals (quartz/feldspar) and dark minerals (biotite/hornblende). It is found worldwide in mountainous or cratonic regions.
