igneous
Granite
Phaneritic intrusive igneous rock (approx. 70 percent SiO2)
Hardness: 6-7 Mohs; Color: Salt and pepper/mottled pink, white, gray, black; Luster: Vitreous to pearly; Structure: Phaneritic (coarse-grained) crystals; Cleavage: None in the bulk rock, but present in individual mineral grains; Specific Gravity: 2.65-2.75.
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper/mottled pink, white, gray, black
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper/mottled pink, white, gray, black; Luster: Vitreous to pearly; Structure: Phaneritic (coarse-grained) crystals; Cleavage: None in the bulk rock, but present in individual mineral grains; Specific Gravity: 2.65-2.75.
Formation & geological history
Formed by the slow crystallization of silica-rich magma beneath the Earth's surface over millions of years. This specimen shows a phaneritic texture characteristic of plutonic environments where slow cooling allows large crystals to grow.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Also used as crushed stone for road base and concrete aggregate. High-quality specimens are collected for geological study.
Geological facts
Granite makes up much of the continuous continental crust. It is primarily composed of quartz, feldspar, and mica. The famous faces of Mount Rushmore are carved into a granite batholith.
Field identification & locations
Identify in the field by its visible interlocking crystals of quartz (clear/gray), feldspar (white/pink), and dark minerals like biotite or hornblende. It is found in large mountain ranges and shield areas globally.
