igneous
Granite
Felsic Intrusive Igneous Rock (SiO2, Al2O3, K2O, Na2O)
Hardness: 6-7 on Mohs scale. Color: Gray, pinkish-white, and black mottled pattern. Luster: Vitreous to dull. Crystal Structure: Phaneritic (coarse-grained) featuring interlocking crystals of quartz, feldspar, and mica. Specific Gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Gray, pinkish-white, and black mottled pattern
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Gray, pinkish-white, and black mottled pattern. Luster: Vitreous to dull. Crystal Structure: Phaneritic (coarse-grained) featuring interlocking crystals of quartz, feldspar, and mica. Specific Gravity: 2.63 to 2.75.
Formation & geological history
Formed through the slow cooling and crystallization of silica-rich magma deep beneath the Earth's surface (plutonic). It is typically associated with continental crust and can range in age from the Precambrian to Cenozoic eras.
Uses & applications
Extensively used in construction as dimension stone, countertops, floor tiles, and as crushed aggregate for road beds and concrete. Also used for monuments and decorative architectural elements.
Geological facts
Granite makes up a significant portion of the Earth's continental crust. Because it forms at great depths, its presence at the surface indicates massive amounts of overlying rock have been eroded away over millions of years. Famous examples include the monoliths of Yosemite National Park.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible, interlocking crystals that are large enough to see without a lens. Often found in mountain ranges or shield areas. Collectors should look for unique mineral inclusions like garnet or tourmaline within the matrix.
