igneous
Granite Cobble
Granite (Felsic Plutonic Rock)
Hardness: 6-7 (Mohs scale); Color: Salt and pepper/pinkish-grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Specific gravity: 2.63-2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Salt and pepper/pinkish-grey
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt and pepper/pinkish-grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Specific gravity: 2.63-2.75
Formation & geological history
Formed through the slow cooling and crystallization of silica-rich magma deep underground (plutonic). This specific specimen has been eroded and smoothed into a 'cobble' or 'river rock' shape by water or glacial action.
Uses & applications
Used widely in construction as crushed stone, dimension stone for countertops and monuments, and as decorative landscaping rock.
Geological facts
Granite makes up the majority of the Earth's continental crust. Over billions of years, it can be pushed to the surface through tectonic uplift and erosion.
Field identification & locations
Identify in the field by its speckled appearance and visible interlocking crystals of quartz (clear/grey) and feldspar (white/pink). It will not be scratched by steel. Found globally in mountainous regions and glacial deposits.
