igneous
Granite
Phaneritic Felsic Igneous Rock
Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black speckles; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: None (though constituent minerals like mica and feldspar have cleavage); Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, white, gray, and black speckles
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black speckles; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: None (though constituent minerals like mica and feldspar have cleavage); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow crystallization of silica-rich magma below the Earth's surface. This specimen appears to be 'pink granite' due to high potassium feldspar content, typically dating from various geological eras including the Precambrian to the Cenozoic.
Uses & applications
Major use in construction as dimension stone (countertops, flooring, monuments) and as crushed stone for road base and concrete aggregate. Highly valued for durability and aesthetics.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota.
Field identification & locations
Identify in the field by its visible interlocking crystals of quartz (glassy), feldspar (pink/white blocks), and mica (shiny black flakes). It cannot be scratched by a steel knife. Common in mountainous regions and shield areas like the Canadian Shield.
