igneous
Granite
Granitoid (composition typically SiO2, Al2O3, K2O, Na2O)
Hardness: 6-7 on Mohs scale; Color: typically white, pink, or gray with darker specks; Luster: dull to vitreous; Crystal structure: phaneritic (large, visible grains); Cleavage: none (fractures irregularly); Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- typically white, pink, or gray with darker specks
- Luster
- dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: typically white, pink, or gray with darker specks; Luster: dull to vitreous; Crystal structure: phaneritic (large, visible grains); Cleavage: none (fractures irregularly); Specific gravity: 2.63 - 2.75
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (intrusive). The process can take millions of years and occurs primarily during the Archean to Cenozoic eras in continental crust/mountain building zones.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. Also used as crushed stone for road base and concrete aggregate.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is one of the hardest substances in the world, second only to diamonds. Mount Rushmore is carved into a massive granite batholith in South Dakota.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. Found globally in continental mountain ranges and shield areas. Collectors look for unique mineral inclusions like tourmaline or garnet.
