igneous
Granite
Phaneritic Igneous Rock (composed mostly of Quartz, Alkali Feldspar, and Plagioclase)
Hardness: 6-7 on Mohs scale; Color: Pinkish-red, white, and grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Distinct in feldspar components; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Pinkish-red, white, and grey
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pinkish-red, white, and grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Distinct in feldspar components; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow crystallization of silica-rich magma beneath the Earth's surface (intrusive). The pink/red color in this specimen is due to potassium feldspar (orthoclase). These rocks can date back billions of years to the Precambrian era.
Uses & applications
Extensively used in construction as dimension stone for countertops, flooring, and curbing. Also used as crushed stone for road base and occasionally polished for use in cemetery monuments.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Famous natural landmarks like Yosemite's Half Dome and Mount Rushmore are made entirely of granite. It is and remains one of the hardest and most durable common building materials.
Field identification & locations
Identify in the field by its 'salt and pepper' or interlocking crystalline appearance where individual mineral grains can be seen without a lens. Common in continental mountain ranges and shields. Collectors look for unique color variations or large phenocrysts (porphyritic texture).
