igneous
Granite
Phaneritic Intrusive Igneous Rock (composed primarily of Quartz, Feldspar, and Mica)
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (white/gray with black specks); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Distinct in feldspar grains, none in quartz; Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Salt and pepper (white/gray with black specks)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (white/gray with black specks); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Distinct in feldspar grains, none in quartz; Specific gravity: 2.63 - 2.75
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface. Granite is part of the continental crust and can date back billions of years (Archean Eon) to more recent tectonic events. It forms in plutons or batholiths deep underground.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stone, curbing, and monuments. It is also a popular aggregate for road construction and a staple for teaching basic geology and mineral identification.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Its name comes from the Latin 'granum', meaning a grain, referring to its coarse-grained texture. Famous landmarks like Mount Rushmore and Yosemite's Half Dome are composed of granite.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and large, interlocked mineral grains. Look for translucent quartz, opaque white or pink feldspar, and shiny black biotite or hornblende. It is ubiquitous in mountainous regions and glacial deposits.
