igneous
Granite
Granite (Silicic Plutonic Rock)
Hardness: 6-7 Mohs; Color: Gray, salt-and-pepper, white; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Perfect on feldspar grains, none on quartz grains; Specific Gravity: 2.63 - 2.75.
- Hardness
- 6-7 Mohs
- Color
- Gray, salt-and-pepper, white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Gray, salt-and-pepper, white; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Perfect on feldspar grains, none on quartz grains; Specific Gravity: 2.63 - 2.75.
Formation & geological history
Formed from the slow cooling and crystallization of magma deep underground (plutonic). Found in continental crust; typical age ranges from Precambrian to Cenozoic.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. It is also used as crushed stone for road base.
Geological facts
Granite makes up the core of most mountain ranges. Mount Rushmore is carved into a massive granite batholith in South Dakota. It is one of the hardest and most durable natural stones.
Field identification & locations
Identify in the field by its 'salt and pepper' look with visible interlocking crystals of quartz (clear/gray), feldspar (white/pink), and mica (black flakes). Commonly found in mountainous regions or shield areas like the Canadian Shield.
