igneous
Granite (Micro-specimen)
Plutonic Igneous Rock (primarily Quartz, Feldspar, and Mica)
Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper (white, grey, and black); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Dependent on mineral inclusions; Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt-and-pepper (white, grey, and black)
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper (white, grey, and black); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Dependent on mineral inclusions; Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. These rocks are found in continental crust and can range from Precambrian to relatively recent geological ages.
Uses & applications
Extensively used in construction (countertops, flooring, monuments) and as crushed stone for road base. Smaller specimens are used for educational geological kits.
Geological facts
Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. Found globally in mountainous regions and shield areas. Collectors look for large, well-defined crystals.
