igneous
Granite
Granite (Phaneritic Acidic Igneous Rock)
Hardness: 6-7 on Mohs scale. Color: White, gray, and pink with dark spots. Luster: Dull to vitreous. Structure: Phaneritic (large, visible crystals). Cleavage: None (grains fracture irregularly). Specific Gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- White, gray, and pink with dark spots
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: White, gray, and pink with dark spots. Luster: Dull to vitreous. Structure: Phaneritic (large, visible crystals). Cleavage: None (grains fracture irregularly). Specific Gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow crystallization of silica-rich magma beneath the Earth's surface. It is an intrusive rock found in continental crust. It can range in age from billions of years (Precambrian) to recently uplifted formations.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments due to its durability and aesthetic appeal. Also used as crushed stone for road base.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. Because it contains trace amounts of uranium, natural granite can emit small amounts of radon gas.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals of quartz (clear/gray), feldspar (white/pink), and mica or hornblende (black). Found globally in mountainous regions and shield areas.
