igneous
Granite
Granite (Alkali feldspar, Plagioclase feldspar, and Quartz)
Hardness: 6-7 (Mohs). Color: Pinkish-gray mottled with white and black translucent grains. Luster: Dull to vitreous. Crystal structure: Phaneritic (coarsegrained holocrystalline). Cleavage: Poor; fractures irregularly. Specific Gravity: 2.63 - 2.75.
- Hardness
- 6-7 (Mohs)
- Color
- Pinkish-gray mottled with white and black translucent grains
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs). Color: Pinkish-gray mottled with white and black translucent grains. Luster: Dull to vitreous. Crystal structure: Phaneritic (coarsegrained holocrystalline). Cleavage: Poor; fractures irregularly. Specific Gravity: 2.63 - 2.75.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (intrusive). Most granite dates back to the Precambrian or Paleozoic eras. It forms the core of many mountain ranges and stable continental cratons.
Uses & applications
Extensively used in construction for dimensional stone, countertops, monuments, and paving. Crushed granite is used as an aggregate in road construction and concrete.
Geological facts
Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. It is one of the hardest and most durable common natural stones used by humans.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible, interlocking mineral crystals (quartz, feldspar, mica). Commonly found in mountainous regions or areas with exposed glacial till. To collect, look for unweathered surfaces showing clear grain boundaries.
