igneous
Granite
Phaneritic Plutonic Felsic Rock
Hardness: 6-7 Mohs; Color: Mottled gray, white, and black with visible crystals; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Non-existent in the rock mass, though individual feldspar grains show cleavage; Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 Mohs
- Color
- Mottled gray, white, and black with visible crystals
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled gray, white, and black with visible crystals; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Non-existent in the rock mass, though individual feldspar grains show cleavage; Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). The large grains indicate a slow cooling process over thousands of years within the Earth's crust.
Uses & applications
Extensively used in construction, countertops, flooring, monuments, and as crushed stone for road base and railroad ballast.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in South Dakota.
Field identification & locations
Identify by its interlocking 'salt and pepper' appearance of quartz (clear/gray), feldspar (white/pink), and mica (black flakes). Commonly found in mountain ranges and areas with exposed continental shields.
