igneous
Granite River Pebble
Granite (Felsic Plutonic Rock)
Hardness: 6-7 Mohs; Color: Light grey with black speckled minerals (Salt and Pepper); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.63 to 2.75
- Hardness
- 6-7 Mohs
- Color
- Light grey with black speckled minerals (Salt and Pepper)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Light grey with black speckled minerals (Salt and Pepper); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow cooling of magma deep beneath the Earth's surface (plutonic). This specific specimen has been shaped and rounded by water erosion in a river or coastal environment.
Uses & applications
Large-scale use in construction, countertops, and landscaping; river pebbles are used in decorative garden design and decorative masonry.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is often found in the roots of mountain ranges. The black spots are likely biotite mica or hornblende, while the light parts are quartz and feldspar.
Field identification & locations
Identify by its crystalline 'speckled' appearance and high hardness (it will scratch glass). Commonly found in glacial tills, riverbeds, and mountainous regions worldwide.
