igneous
Granite
Phaneritic Plutonic Igneous Rock (composed of Quartz, Feldspar, and Mica)
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (gray, white, and black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Cleavage: No overall cleavage (though individual minerals within it like mica have perfect cleavage); Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (gray, white, and black)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (gray, white, and black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Cleavage: No overall cleavage (though individual minerals within it like mica have perfect cleavage); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed through the slow crystallization of silica-rich magma below the Earth's surface (intrusive). They can range from Archean to Cenozoic ages and are found in the continental crust, particularly in mountain belts and cratons.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, monuments, and as crushed stone for road base and concrete aggregate.
Geological facts
Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a granite batholith in the Black Hills of South Dakota. It is one of the hardest and most durable natural stones available.
Field identification & locations
Identify in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals of quartz (translucent gray) and feldspar (white/pink). Found in large outcrops or as erratics. Collectors look for unique mineral inclusions or rare colors.
