igneous
Granite Water-Worn Pebble
Phaneritic intrusive igneous rock (Felsic)
Hardness: 6-7 Mohs; Color: Speckled pink, cream, and grey; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Specific gravity: 2.63-2.75.
- Hardness
- 6-7 Mohs
- Color
- Speckled pink, cream, and grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Speckled pink, cream, and grey; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Specific gravity: 2.63-2.75.
Formation & geological history
Formed by the slow cooling of silica-rich magma deep underground. This specific specimen has been smoothed and rounded by the mechanical weathering of water in a river or coastal environment.
Uses & applications
Used extensively in construction (countertops, flooring, monuments) and as crushed stone for road base. Smooth pebbles are often used in landscaping or as decorative garden stones.
Geological facts
Granite makes up much of the Earth's continental crust. Because it is so hard and durable, it can survive long journeys down rivers, becoming perfectly rounded like the specimen in the image.
Field identification & locations
Identify by its salt-and-pepper or speckled appearance with visible interlocking crystals. Common in glacial till and riverbeds across North America and Europe.
