igneous
Granite
Phaneritic Felsic Igneous Rock (composed primarily of Quartz, Feldspar, and Mica)
Hardness: 6-7 (Mohs scale); Color: Salt and pepper/speckled grey, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals); Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Salt and pepper/speckled grey, white, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt and pepper/speckled grey, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals); Specific gravity: 2.63 - 2.75
Formation & geological history
Formed through the slow crystallization of magma below the Earth's surface in continental crust plumes. These intrusive rocks can be hundreds of millions of years old and are exposed after long periods of erosion.
Uses & applications
Commonly used in construction for countertops, floor tiles, paving stones, and memorial monuments due to its durability and resistance to weathering.
Geological facts
Granite makes up much of 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 interlocking visible grains of glassy quartz, opaque white/pink feldspar, and black mica flakes. It is very hard and will scratch glass easily.
