igneous
Granite Water-Worn Pebble
Phaneritic intrusive igneous rock (Quartz, Feldspar, Mica)
Hardness: 6-7 Mohs; Color: Gray and pink speckled; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible crystals); Cleavage: None (fractures); Specific gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Gray and pink speckled
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Gray and pink speckled; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible crystals); Cleavage: None (fractures); Specific gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground. This specific specimen has been rounded and smoothed by mechanical weathering in a high-energy aquatic environment like a river or beach.
Uses & applications
Larger deposits are used for construction, countertops, and monuments; as a pebble, it is primarily used for landscaping or decorative gravel.
Geological facts
Granite is the most common rock found in the Earth's continental crust. Because of its hardness and resistance to erosion, it often forms the core of many mountain ranges.
Field identification & locations
Identify by the 'salt and pepper' appearance of interlocking crystals and its rounded, water-smoothed shape. Commonly found in riverbeds, glacial tills, and along coastal areas.
