igneous
Granite
Phaneritic Felsic Igneous Rock (primarily SiO2, Al2O3, K2O, Na2O)
Hardness: 6 to 7 on the Mohs scale. Color: Salt-and-pepper appearance with shades of white, pink, and grey. Luster: Vitreous to pearly. Crystal structure: Phaneritic (coarse-grained) with interlocking crystals of quartz, feldspar, and mica.…
- Hardness
- 6 to 7 on the Mohs scale
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6 to 7 on the Mohs scale. Color: Salt-and-pepper appearance with shades of white, pink, and grey. Luster: Vitreous to pearly. Crystal structure: Phaneritic (coarse-grained) with interlocking crystals of quartz, feldspar, and mica. Cleavage: Indistinct in the mass, but feldspar components show two directions at 90 degrees. Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed through the slow crystallization of magma below the Earth's surface (intrusive). Geological ages vary widely from the Archean Eon to the Cenozoic. It is commonly found in the continental crust within batholiths and mountain ranges.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and masonry. It is also used in monument carving, curling stones, and as a popular landscaping material.
Geological facts
Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota. Historically, it was used by Ancient Egyptians to build the internal chambers of the Great Pyramid of Giza.
Field identification & locations
Identify in the field by its speckled, interlocking crystal texture where individual minerals (clear quartz, white/pink feldspar, black biotite) are visible to the naked eye. It is found in tectonic regions and ancient shield areas like the Canadian Shield or the Appalachians.
