igneous
Granite
Phaneritic plutonic igneous rock (Granite)
Hardness: 6-7 on Mohs scale; Color: Mottled pink, gray, black, and white; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained) with interlocking crystals of quartz, feldspar, and mica; Cleavage: None (fractures irregularly); Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, gray, black, and white
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled pink, gray, black, and white; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained) with interlocking crystals of quartz, feldspar, and mica; Cleavage: None (fractures irregularly); Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface in large intrusions called batholiths. It usually dates back to Precambrian or Paleozoic eras in continental crust.
Uses & applications
Widely used for dimension stone, countertops, flooring, monuments, paving, and as crushed stone for road construction and concrete aggregate.
Geological facts
Granite makes up a large portion of the continental crust. Because it is so hard and durable, it is essentially the 'foundation' of the continents. Mount Rushmore is carved into a granite batholith.
Field identification & locations
Identify by its salt-and-pepper appearance and visible visible crystals. It is found in large mountain ranges and shield areas like the Canadian Shield or the Appalachian Mountains. Look for the presence of translucent quartz grains and pink/white feldspar.
