igneous
Granite
Intrusive Felsic Igneous Rock
Hardness: 6-7 on Mohs scale. Color: Speckled gray, white, and black (salt-and-pepper pattern). Luster: Dull to vitreous (glassy quartz grains). Texture: Phaneritic (medium to coarse-grained mineral grains). Cleavage: Non-uniform, breaks unevenly. Specific gravity: ~2.65-2.75 g/cm3.
- Hardness
- 6-7 on Mohs scale
- Color
- Speckled gray, white, and black (salt-and-pepper pattern)
- Luster
- Dull to vitreous (glassy quartz grains)
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Speckled gray, white, and black (salt-and-pepper pattern). Luster: Dull to vitreous (glassy quartz grains). Texture: Phaneritic (medium to coarse-grained mineral grains). Cleavage: Non-uniform, breaks unevenly. Specific gravity: ~2.65-2.75 g/cm3.
Formation & geological history
Formed from the slow crystallization of silica-rich magma deep underground beneath continental crust. This slow cooling allows individual mineral crystals (quartz, plagioclase feldspar, potassium feldspar, biotite, and hornblende) to grow large enough to see with the naked eye.
Uses & applications
Extensively used as building stones, curb blocks, paving stones, kitchen countertops, monuments, and crushed stone for road construction due to its high durability and resistance to weathering.
Geological facts
Granite makes up the majority of Earth's continental crust. Mount Rushmore, the Great Pyramid of Giza's inner chambers, and Yosemite's El Capitan are all composed of granite.
Field identification & locations
Identified in the field by its distinct speckling of interlocking quartz (translucent glassy grey), feldspar (white/pink blocky grains), and dark ferromagnesian minerals (black flakes of biotite or amphibole). Found widely in mountainous areas and shield regions globally.
