igneous
Granite (River-worn)
Phaneritic Igneous Rock (primarily Quartz, Feldspar, and Mica)
Hardness: 6-7 (Mohs scale); Color: Mottled pink, white, gray, and black; Luster: Dull to vitreous; Structure: Phaneritic (visible crystals); Cleavage: Dependent on mineral (feldspar has 2 planes); Specific Gravity: 2.63-2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled pink, white, gray, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled pink, white, gray, and black; Luster: Dull to vitreous; Structure: Phaneritic (visible crystals); Cleavage: Dependent on mineral (feldspar has 2 planes); Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling and crystallization of felsic magma deep beneath the Earth's surface (plutonic). This specific specimen shows rounding and smoothing characteristic of water erosion in a river or beach environment.
Uses & applications
Commonly used in large scale construction, counter tops, and decorative landscaping. Small rounded pebbles are used in Zen gardens and aquarium decor.
Geological facts
Granite is the most common rock found on the Earth's continental crust. Its name comes from the Latin word 'granum', meaning a grain, in reference to its coarse-grained structure.
Field identification & locations
Identify in the field by looking for a 'salt and pepper' or mottled appearance with visible interlocking grains of different colors. It is extremely common in mountainous regions and riverbeds.
