igneous
Granite
Granite (Felsic Plutonic Rock)
Hardness: 6-7 (Mohs scale); Color: Mottled salt-and-pepper (white, gray, black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) containing quartz, feldspar, and mica; Specific Gravity: 2.63 to 2.75.
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled salt-and-pepper (white, gray, black)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled salt-and-pepper (white, gray, black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) containing quartz, feldspar, and mica; Specific Gravity: 2.63 to 2.75.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (intrusive). They are found in the continental crust of every era from Precambrian to relatively recent Cenozoic formations.
Uses & applications
Used extensively in construction for countertops, floor tiles, paving stones, curbing, monuments, and as crushed stone for road base.
Geological facts
Granite makes up a large part of the continental crust. Because it is intrusive, it cools so slowly that individual mineral crystals are visible to the naked eye.
Field identification & locations
Identify by its interlocking 'salt and pepper' crystalline texture. Quartz usually appears as glassy gray grains, feldspar as opaque white or pink, and mica as shiny black flakes. Common in mountain ranges and shields.
