igneous
Granite Pebble (River Rock)
Phaneritic Felsic Igneous Rock
Hardness: 6-7 Mohs; Color: Mottled cream, tan, and grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Indistinct; Specific gravity: Approx 2.6-2.7.
- Hardness
- 6-7 Mohs
- Color
- Mottled cream, tan, and grey
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled cream, tan, and grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Indistinct; Specific gravity: Approx 2.6-2.7.
Formation & geological history
Formed through the slow cooling of silica-rich magma deep underground. This specific specimen has been shaped and smoothed by fluvial (river) erosion or shoreline Wave action over a period of many years to centuries.
Uses & applications
Used primarily for landscaping, decorative garden stones, and as aquarium substrate. In bulk, granite is used in construction and for kitchen countertops.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Because of its hardness, it survives long journeys down rivers, eventually becoming these smooth, oval-shaped 'worry stones'.
Field identification & locations
Identify by its speckled 'salt and pepper' appearance and its extreme hardness; it will scratch glass and cannot be scratched by a steel knife. Commonly found in riverbeds, glacial deposits, and beaches.
