igneous
Granite
Phaneritic Plutonic Felsic Rock (SiO2 > 69%)
Hardness: 6-7 Mohs; Color: Salt and pepper (white/pink feldspar, clear/grey quartz, black mica/amphibole); Luster: Dull to vitreous; Crystal Structure: Phaneritic (visible interlocking crystals); Cleavage: None (fractures), though minerals within have cleavage; Specific Gravity: 2.63 to 2.75
- Hardness
- 6-7 Mohs
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (white/pink feldspar, clear/grey quartz, black mica/amphibole); Luster: Dull to vitreous; Crystal Structure: Phaneritic (visible interlocking crystals); Cleavage: None (fractures), though minerals within have cleavage; Specific Gravity: 2.63 to 2.75
Formation & geological history
Formed by the slow crystallization of magma below the Earth's surface (intrusive). Most granite dates from the Precambrian or Paleozoic eras, forming the core of continental plates.
Uses & applications
Extensively used in construction (countertops, floor tiles, paving stones), monuments, curbing, and as aggregate for roads.
Geological facts
Granite makes up a large portion of the Earth's continental crust. El Capitan in Yosemite National Park is a massive single exposure of granite.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals that are roughly equal in size. It is found globally in mountainous regions or where ancient shields are exposed. No visible layering or fossils will be present.
