igneous
Granite
Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)
Hardness: 6–7 on Mohs scale; Color: Speckled gray, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (large, visible interlocking grains); Cleavage: Indistinct; Specific gravity: 2.63 - 2.75
- Hardness
- 6–7 on Mohs scale
- Color
- Speckled gray, white, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6–7 on Mohs scale; Color: Speckled gray, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (large, visible interlocking grains); Cleavage: Indistinct; Specific gravity: 2.63 - 2.75
Formation & geological history
Formed through the slow crystallization of magma below the Earth's surface (intrusive). They are typically found in batholiths and continental crust, with ages ranging from billions of years (Precambrian) to more recent tectonic events.
Uses & applications
Extensively used in construction as dimension stone, floor tiles, kitchen countertops, and as crushed stone for road base or railway ballast.
Geological facts
Granite is the most common rock in the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota.
Field identification & locations
Identify in the field by its interlocking 'salt and pepper' crystalline texture and extreme hardness (cannot be scratched by a steel blade). Common in mountain ranges and eroded shield areas worldwide.
