igneous
Granite
Granite (Felsic Plutonic Rock)
Hardness: 6-7 (Mohs scale); Color: Mottled grey, pink, and white; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (grains have individual cleavage planes); Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled grey, pink, and white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled grey, pink, and white; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (grains have individual cleavage planes); Specific gravity: 2.63 - 2.75
Formation & geological history
Formed from the slow cooling and crystallization of magma deep beneath the Earth's surface. It is an intrusive rock typically associated with continental crust and can range from Precambrian to Cenozoic in age.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. It is also often crushed for road base and railroad ballast.
Geological facts
Granite is the primary component of the Earth's continental crust. El Capitan in Yosemite National Park is one of the world's most famous monolithic granite formations.
Field identification & locations
Identify in the field by looking for a 'salt and pepper' appearance with visible crystals of quartz, feldspar, and mica. It is commonly found in mountain ranges and eroded shield areas. Collectors should look for unique porphyritic textures or rare accessory minerals.
