igneous
Granite
Phaneritic Igneous Rock (composed of quartz, alkali feldspar, and plagioclase)
Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black speckled appearance; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, white, gray, and black speckled appearance
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black speckled appearance; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). It is found in continental crust and is common in mountain ranges and ancient shield areas, ranging from billions of years old to relatively recent geological timeframes.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. It is also crushed into aggregate for road building and concrete.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Famous landmarks like Mount Rushmore and Yosemite's Half Dome are composed of granite. It is one of the hardest and most durable natural stones available.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is ubiquitous in mountainous terrains and gravel pits. Collectors look for unique colorations or large feldspar phenocrysts (porphyritic granite).
