igneous
Granite
Phaneritic Igneous Rock (composed of Quartz, Feldspar, and Mica/Amphibole)
Hardness: 6-7 (Mohs scale); Color: Pinkish-gray with black speckles; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Dependent on mineral grains (Feldspar has 2 planes at 90 degrees).
- Hardness
- 6-7 (Mohs scale)
- Color
- Pinkish-gray with black speckles
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Pinkish-gray with black speckles; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Dependent on mineral grains (Feldspar has 2 planes at 90 degrees).
Formation & geological history
Formed through the slow crystallization of magma below the Earth's surface (intrusive). Most granite dates to the Precambrian or Paleozoic eras. It forms in continental crust above subduction zones or in mountain-building regions.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments due to its durability and aesthetic appeal. Small specimens are used in educational collections.
Geological facts
Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith. It is one of the hardest and most durable common stones.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and large, interlocked crystals. It is found globally in mountainous terrains and shields. Collectors look for unique color variations or large crystal inclusions.
