igneous
Granite
Granite (Phaneritic Igneous Rock)
Hardness: 6-7 Mohs; Color: Salt and pepper (gray, white, pink, black); Luster: Vitreous to dull; Crystal structure: Coarse-grained phaneritic; Cleavage: Improper (breaks unevenly); Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper (gray, white, pink, black)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (gray, white, pink, black); Luster: Vitreous to dull; Crystal structure: Coarse-grained phaneritic; Cleavage: Improper (breaks unevenly); Specific gravity: 2.63 - 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). Most granite dates from the Precambrian or Paleozoic eras, though it forms in any era where continental crust thickens.
Uses & applications
Extensively used in construction for curbing (as seen in the image), countertops, floor tiles, paving stones, and monuments due to its durability.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. It is the most common plutonic rock found in the crust.
Field identification & locations
Identify by its 'salt and pepper' appearance with visible interlocking crystals of quartz (clear/gray), feldspar (white/pink), and mica (shiny black flakes). Commonly found in mountain ranges and ancient shield areas.
