igneous
Granite
Phaneritic Felsic Igneous Rock (primarily Quartz, Alkali Feldspar, and Plagioclase)
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white, gray, pink, and black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Distinct in feldspars, none in quartz; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 Mohs
- Color
- Salt-and-pepper (white, gray, pink, and black)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white, gray, pink, and black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Distinct in feldspars, none in quartz; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow cooling and crystallization of silica-rich magma deep underground (plutonic), typically associated with continental crust formation over millions of years.
Uses & applications
A major construction material used for countertops, floor tiles, curbing, monuments, and as crushed stone for road base and concrete aggregate.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is extremely durable and resistant to acid rain, which is why it has been used to build some of the world's most famous structures, like the Great Pyramid of Giza (interior) and Mount Rushmore.
Field identification & locations
Identify by its interlocking 'salt-and-pepper' mineral grains which are large enough to see with the naked eye. It is found in large mountain ranges and old continental shields. For collectors, look for unique colors or large 'pegmatitic' crystals.
