igneous
Granite
Phaneritic intrusive igneous rock (composition: Quartz, Feldspar, Mica)
Hardness: 6-7 Mohs; Color: Mottled white, pink, grey, and black; Luster: Dull to pearly; Structure: Phaneritic (large, visible crystals); Cleavage: Predominantly feldspar cleavage planes; Specific Gravity: 2.63 to 2.75
- Hardness
- 6-7 Mohs
- Color
- Mottled white, pink, grey, and black
- Luster
- Dull to pearly
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled white, pink, grey, and black; Luster: Dull to pearly; Structure: Phaneritic (large, visible crystals); Cleavage: Predominantly feldspar cleavage planes; Specific Gravity: 2.63 to 2.75
Formation & geological history
Formed by the slow cooling of silica-rich magma deep underground (plutonic). Most terrestrial granite formed during the Precambrian and Paleozoic eras in continental crust environments.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments due to its durability and aesthetic appeal.
Geological facts
Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in South Dakota.
Field identification & locations
Identified by its speckled 'salt and pepper' appearance and hardness. It is commonly found in mountain ranges and ancient shield areas like the Canadian Shield. Collectors look for large crystals or unique color variations.
