igneous
Granite
Phaneritic Felsic Igneous Rock
Hardness: 6-7 on Mohs scale; Color: Pink, grey, and black salt-and-pepper appearance; Luster: Vitreous to dull; Structure: Phaneritic (coarse-grained); Cleavage: None (individual minerals have cleavage, the rock does not); Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, grey, and black salt-and-pepper appearance
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, grey, and black salt-and-pepper appearance; Luster: Vitreous to dull; Structure: Phaneritic (coarse-grained); Cleavage: None (individual minerals have cleavage, the rock does not); Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow crystallization of silica-rich magma below Earth's surface (plutonic). It is primarily composed of quartz, alkali feldspar, and plagioclase, with minor amounts of mica and amphiboles. Often Precambrian to Cenozoic in age.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stone, curbing, and monuments. Extremely durable and resistant to weathering.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. It is one of the hardest and most common rocks found in nature.
Field identification & locations
Identify by its interlocking 'salt-and-pepper' mineral crystals that are large enough to see with the naked eye. Commonly found in mountainous regions or as glacial erratics (rounded river/field stones). Collectors look for unique mineral inclusions or structural patterns.
