igneous
Granite
Granite (composed of quartz, potassium feldspar, plagioclase, and mica/biotite)
Hardness: 6-7 on the Mohs scale. Color: Pinkish-tan feldspar mixed with translucent grey smoky quartz and dark biotite or hornblende inclusions. Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained, interlocking crystalline texture).…
- Hardness
- 6-7 on the Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on the Mohs scale. Color: Pinkish-tan feldspar mixed with translucent grey smoky quartz and dark biotite or hornblende inclusions. Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained, interlocking crystalline texture). Cleavage: Feldspars show distinct cleavage planes, quartz has conchoidal fracture. Specific Gravity: 2.65-2.75.
Formation & geological history
Formed deep beneath the Earth's crust through the slow cooling and crystallization of felsic magma. This slow cooling process allows individual mineral crystals of quartz, feldspar, and mica to grow large enough to be visible to the naked eye. Found in continental crust formations spanning Precambrian to Cenozoic ages.
Uses & applications
Extensively used as a dimension stone in construction, counter tops, flooring, monuments, and paving blocks. Coarser or weathered specimens are crushed for aggregate. It is also collected by mineral enthusiasts as a classic rock specimen.
Geological facts
Granite makes up a major portion of the Earth's continental crust. Mount Rushmore, the base of the Statue of Liberty, and the dramatic peaks of Yosemite Valley are all formed from massive granite formations.
Field identification & locations
Can be identified in the field by its coarse, visible interlocking grains of pink/cream feldspar, glassy grey quartz, and dark specks of mica. Extremely abundant worldwide in continental shields and mountain ranges.
