igneous
Granite
Phaneritic Felsic Igneous Rock
Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black mottled appearance; Luster: Dull to vitreous (glassy); Crystal Structure: Phaneritic (coarse-grained) consisting mainly of quartz, K-feldspar, and plagioclase; Cleavage: None (fractures irregularly); Specific Gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, white, gray, and black mottled appearance
- Luster
- Dull to vitreous (glassy)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black mottled appearance; Luster: Dull to vitreous (glassy); Crystal Structure: Phaneritic (coarse-grained) consisting mainly of quartz, K-feldspar, and plagioclase; Cleavage: None (fractures irregularly); Specific Gravity: 2.63 to 2.75.
Formation & geological history
Formed through the slow crystallization of silica-rich magma beneath the Earth's surface (intrusive). Most granite plutons date from the Precambrian to Cenozoic eras, often associated with continental crust formation and mountain-building events.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stone, and curbing. It is also used for monuments, gravestones, and as an aggregate in road construction. High-quality specimens with unique patterns are sought after by hobbyist collectors for tumbling.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. Because it is so hard and durable, it was the preferred building material for many ancient Egyptian pyramids and temples.
Field identification & locations
Identify in the field by its 'salt and pepper' or mottled look and visible interlocking crystals. You can find it in continental mountain ranges or as glacial erratics in gravel pits. It will not be scratched by a steel knife and will not fizz with acid.
