igneous
Granite
Phaneritic plutonic rock (Quartz, Alkali Feldspar, and Plagioclase)
Hardness: 6-7 on Mohs scale. Color: Mottled pink, white, and grey with black specks. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained). Cleavage: Poor; fractures along mineral boundaries. Specific gravity: 2.63 - 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, white, and grey with black specks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled pink, white, and grey with black specks. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained). Cleavage: Poor; fractures along mineral boundaries. Specific gravity: 2.63 - 2.75.
Formation & geological history
Formed from the slow cooling and crystallization of magma deep within the Earth's crust (intrusive). Most granite dates from the Precambrian to Cenozoic eras, often associated with mountain-building events.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments due to its durability. Also used as crushed stone for road base and railroad ballast.
Geological facts
Granite makes up a large part of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in South Dakota, and the 'pink' color is usually due to an abundance of potassium feldspar.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is ubiquitous in continental mountain ranges. For collectors, look for unique mineral inclusions like large garnets or distinct porphyritic textures.
