igneous
Granite Cobble
Granite (Phaneritic Igneous Rock)
Hardness: 6-7 Mohs; Color: Pink, grey, and white mottled; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Composition: Quartz, Potassium Feldspar, and Plagioclase.
- Hardness
- 6-7 Mohs
- Color
- Pink, grey, and white mottled
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Pink, grey, and white mottled; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Composition: Quartz, Potassium Feldspar, and Plagioclase.
Formation & geological history
Formed through the slow crystallization of magma below the Earth's surface (intrusive). This specific specimen shows signs of fluvial or glacial transport, resulting in its rounded 'cobble' shape.
Uses & applications
Used in construction as crushed stone, dimension stone for countertops and monuments, and occasionally as decorative landscaping rock.
Geological facts
Granite is the most common rock found in the Earth's continental crust. The pink hue in this specimen is caused by the presence of Orthoclase (potassium feldspar).
Field identification & locations
Identify in the field by its speckled 'salt and pepper' appearance and visible crystal grains. It is extremely common in glacial till and riverbeds across North America.
