igneous
Granite
Phaneritic Plutonic Felsic Rock (SiO2, KAlSi3O8, NaAlSi3O8)
Hardness: 6-7 Mohs; Color: Mottled grey, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse crystals visible to eye); Specific Gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Mottled grey, white, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled grey, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse crystals visible to eye); Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. Primarily composed of quartz, feldspar, and mica. Formation ages can range from billions of years (cratons) to relatively young geological periods.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stone, monuments, and as crushed stone for road base.
Geological facts
Granite makes up a large part of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. It is one of the hardest and most durable common stones, resistant to weathering.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking mineral grains. Commonly found in mountainous regions or where ancient continental crust is exposed. Look for the presence of translucent quartz and shiny mica flakes.
