Rock Identifier
Granite (Phaneritic Plutonic Igneous Rock (composed of quartz, alkali feldspar, and plagioclase)) — igneous
igneous

Granite

Phaneritic Plutonic Igneous Rock (composed of quartz, alkali feldspar, and plagioclase)

Hardness: 6-7 on Mohs scale; Color: Pink, white, and grey speckled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained coarse crystals visible to the naked eye); Cleavage: Variable based on mineral (feldspar has 2 directions, quartz has none); Specific gravity: 2.63 to 2.75.

Hardness
6-7 on Mohs scale
Color
Pink, white, and grey speckled
Luster
Vitreous to dull
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Physical properties

Hardness: 6-7 on Mohs scale; Color: Pink, white, and grey speckled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained coarse crystals visible to the naked eye); Cleavage: Variable based on mineral (feldspar has 2 directions, quartz has none); Specific gravity: 2.63 to 2.75.

Formation & geological history

Formed from the slow crystallization of silica-rich magma beneath the Earth's surface (intrusive). They are found in continental crust across all geological ages, notably in mountain-building belts.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Also used as crushed stone for road base and railroad ballast.

Geological facts

Granite is the primary rock of the Earth's continental crust. El Capitan in Yosemite National Park is one of the most famous granite monoliths in the world. It is much harder than marble and resistant to acid rain.

Field identification & locations

Identify by its interlocking 'salt and pepper' appearance with visible crystals. Look for the pink/salmon color of potassium feldspar. It is found in large outcrops called batholiths. Collectors should look for unique proportions of biotite or hornblende (the black spots).

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