igneous
Granite
Phaneritic Granitoid (Primary minerals: Quartz SiO2, Feldspar KAlSi3O8, and Biotite/Mica)
Hardness: 6-7 Mohs; Color: Pink, white, gray, and black mottled patterns; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (individual crystals show cleavage, the rock does not); Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 Mohs
- Color
- Pink, white, gray, and black mottled patterns
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Pink, white, gray, and black mottled patterns; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (individual crystals show cleavage, the rock does not); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). The pink color indicates a high concentration of potassium feldspar. It can range in age from billions of years (Precambrian) to relatively recent eras.
Uses & applications
Extensively used in construction for countertops, monuments, floor tiles, and paving stones. It is also crushed into aggregate for road building and landscaping.
Geological facts
Granite makes up the majority of the Earth's continental crust. Mount Rushmore and the Egyptian pyramids contain significant amounts of granite or granite-like rock. It is one of the hardest and most durable common substances on the planet.
Field identification & locations
Identified in the field by its 'salt and pepper' appearance and visible interlocking crystals of different colors. It is found in large mountain ranges and continental shields globally. Collectors look for 'pegmatite' varieties with exceptionally large crystals.
