igneous
Granite
Phaneritic plutonic igneous rock (SiO2 range 65-75%)
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (gray, white, black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Specific gravity: 2.63-2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (gray, white, black)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (gray, white, black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Specific gravity: 2.63-2.75
Formation & geological history
Formed by the slow crystallization of magma below Earth's surface. It is a plutonic rock that cools over thousands of years, allowing large mineral grains to grow. Found in continental crust and mountain ranges.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stone, monuments, and as crushed stone for road base and concrete aggregate.
Geological facts
Granite is one of the hardest substances in the world, second only to diamonds. It makes up a large portion of the Earth's continental crust and is the primary rock found in famous locations like Yosemite and Mount Rushmore.
Field identification & locations
Identify in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. It is usually found in large mountainous outcrops or as rounded river cobbles.
