igneous
Granite
Phaneritic plutonic rock (SiO2 primary)
Hardness: 6-7 Mohs; Color: Grey, pink, white, and black speckled; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Cleavage: None (fractures); Specific Gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Grey, pink, white, and black speckled
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Grey, pink, white, and black speckled; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Cleavage: None (fractures); Specific Gravity: 2.63-2.75
Formation & geological history
Formed by the slow cooling and crystallization of silica-rich magma deep within the Earth's crust over millions of years. Common in continental crust and mountain ranges from various geological eras.
Uses & applications
Extensively used in construction for countertops, flooring, monuments, paving stones, and as aggregate for roads. Value in collecting is generally low unless it contains unique mineral inclusions.
Geological facts
Granite makes up the bulk of the Earth's continental crust. It is one of the hardest natural stones, which is why it has been used for monuments since ancient Egypt. Mount Rushmore is carved into a massive granite batholith.
Field identification & locations
Identify by its salt-and-pepper appearance and visible individual crystals of quartz, feldspar, and mica. It is found globally in large plutons (batholiths) and mountain cores. Check for hardness (will scratch glass).
