Igneous
Granite
Granite (Felsic Plutonic Rock)
Hardness: 6-7 (Mohs scale); Color: Salt-and-pepper (combination of white, grey, black, and sometimes pink); Luster: Phaneritic (visible crystals), vitreous to dull; Crystal structure: Coarse-grained granular; Cleavage: None (fractures irregularly); Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 (Mohs scale)
- Luster
- Phaneritic (visible crystals), vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt-and-pepper (combination of white, grey, black, and sometimes pink); Luster: Phaneritic (visible crystals), vitreous to dull; Crystal structure: Coarse-grained granular; Cleavage: None (fractures irregularly); Specific gravity: 2.63 - 2.75
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (intrusive). The coarseness of the grains indicates it cooled very slowly over thousands of years. It can date from the Archean Eon to the Cenozoic Era, commonly appearing in the continental crust.
Uses & applications
Used extensively in construction for dimension stone, countertops, floor tiles, and paving. It is also utilized in heavy engineering as aggregate for road base and railroad ballast. Small polished specimens are common in beginner rock collections.
Geological facts
Granite is the primary component of Earth's continental crust and is unique to Earth among the planets in our solar system. Mount Rushmore and Yosemite's Half Dome are famous landmarks carved from granite plutons.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and interlocking visible crystals of quartz (clear/grey) and feldspar (white/pink). Found frequently in glaciated areas as 'glacial erratics' or in mountain ranges. It is very resistant to weathering.
