igneous
Granite
Granite (phaneritic intrusive igneous rock consisting of 20-60% quartz, orthoclase/plagioclase feldspar, and mica/amphibole)
Hardness: 6-7 on Mohs scale; Color: Pink, gray, white with black specks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Irregular fracture; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, gray, white with black specks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, gray, white with black specks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Irregular fracture; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed through the slow crystallization of silica-rich magma below Earth's surface. It can date from almost any geological age, though most prevalent in the Precambrian. Found in continental crust and mountain ranges.
Uses & applications
Major use in construction as dimension stone, monuments, gravel/aggregate, countertops, and floor tiles. High-quality colored variants are used in ornamental carving.
Geological facts
Granite makes up the majority of the Earth's continental crust. Because it is so hard, it allows mountains like the Himalayas and the Alps to reach their extreme heights without collapsing under their own weight.
Field identification & locations
Identify by its 'salt and pepper' appearance and large interlocking crystals of quartz and feldspar. Found globally in batholiths and mountain cores. Field collectors should look for its inability to be scratched by a steel blade.
