igneous
Granite (Pink/Red Granite)
Phaneritic Igneous Rock (primarily SiO2, KAlSi3O8, NaAlSi3O8)
Hardness: 6-7 on Mohs scale; Color: Mottled pink, grey, and black; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained) containing visible crystals of K-feldspar, quartz, and mica; Specific Gravity: 2.63-2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, grey, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled pink, grey, and black; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained) containing visible crystals of K-feldspar, quartz, and mica; Specific Gravity: 2.63-2.75.
Formation & geological history
Formed from the slow cooling and solidification of molten magma deep beneath the Earth's surface (plutonic). Found in continental crust plates; can date back billions of years to the Precambrian era.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Also used as crushed stone/aggregate for road base and railway ballast.
Geological facts
Mt. Rushmore is carved into a granite batholith. The pink color in this specific specimen is caused by a high concentration of Potassium Feldspar (Orthoclase).
Field identification & locations
Identify in the field by the 'salt and pepper' or multicrystalline locked texture where grains are visible to the naked eye. Found globally in mountainous regions and shield areas like the Canadian Shield or the Scottish Highlands.
