igneous
Granite Cobble
Phaneritic Felsic Igneous Rock (Granite)
Hardness: 6-7 on Mohs scale; Color: Mottled gray, white, and black; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained visible crystals); Composition: Principally Quartz, Feldspar, and Mica; Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled gray, white, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled gray, white, and black; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained visible crystals); Composition: Principally Quartz, Feldspar, and Mica; Specific gravity: 2.63 - 2.75
Formation & geological history
Formed from the slow cooling and crystallization of molten magma deep beneath the Earth\'s surface. This specific specimen has been smoothed and rounded by water erosion (fluvial or glacial processes) over thousands of years.
Uses & applications
In this rounded form, they are used as decorative landscaping stones and river rock. In its raw form, granite is essential for construction (countertops, monuments, and aggregate).
Geological facts
Granite makes up a large portion of the Earth\'s continental crust. Because it contains radioactive elements like thorium and uranium, high-density granite can actually emit small, harmless amounts of radon gas.
Field identification & locations
Identify by its 'salt and pepper' appearance and the presence of glass-like translucent quartz grains mixed with opaque white feldspar. Commonly found in riverbeds, glacial moraines, and coastal beaches where water has weathered the edges of the rock.
