igneous
Granite (with Quartz and Mica)
Phaneritic Felsic Igneous Rock
Hardness: 6-7 (Mohs); Color: Mottled white, grey, and reddish-brown; Luster: Vitreous to pearly; Structure: Phaneritic (coarse-grained); Cleavage: Poor; Specific Gravity: 2.63 to 2.75
- Hardness
- 6-7 (Mohs)
- Color
- Mottled white, grey, and reddish-brown
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 (Mohs); Color: Mottled white, grey, and reddish-brown; Luster: Vitreous to pearly; Structure: Phaneritic (coarse-grained); Cleavage: Poor; Specific Gravity: 2.63 to 2.75
Formation & geological history
Formed through the slow cooling and crystallization of silica-rich magma deep within the Earth's crust (plutonic formation). These rocks typically date back to the Precambrian or Paleozoic eras when mountain-building events occurred.
Uses & applications
Extensively used in construction for countertops, floor tiles, and curbing. In industry, it is used as crushed stone for road base. Specimens with distinct crystal clusters are popular for mineral collecting and paperweights.
Geological facts
Granite is the most common rock found in the continental crust and forms the core of many mountain ranges. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz (clear/grey) and feldspar (white/pink). Look for the reflective flashes of mica flakes. Common in mountainous regions and glacial deposits.
