Igneous
Granite
Phaneritic Felsic Intrusive Rock (Granite)
Hardness: 6-7 Mohs; Color: Pinkish-red, grey, and black mottled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Perfect on feldspar grains; Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 Mohs
- Color
- Pinkish-red, grey, and black mottled
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Pinkish-red, grey, and black mottled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Perfect on feldspar grains; Specific gravity: 2.63 - 2.75
Formation & geological history
Formed from the slow crystallization of silica-rich magma deep underground (plutonic). This process allows large crystals of quartz, feldspar, and mica to grow. It is common in continental crust and often dates back hundreds of millions to billions of years.
Uses & applications
Used extensively in construction for countertops, floor tiles, paving stones, curbing, monuments, and as aggregate for roads.
Geological facts
Granite makes up the core of most continental mountain ranges. It is one of the hardest and most durable natural stones, which is why it has been used in architecture since Ancient Egypt. The pink/red color comes from potassium feldspar (orthoclase).
Field identification & locations
Identify by looking for a 'salt and pepper' or multicomponent interlocking crystal texture. It will not scratch easily with a steel knife. It is common in batholiths and mountain cores across the globe, such as the Sierra Nevada or the Scottish Highlands.
