metamorphic
River Pebble (Gneiss or Quartzite mixture)
Metamorphic rock (Commonly Gneissic)
Hardness: 6-7 on Mohs scale; Color: Gray, black, and white banding/mottling; Luster: Dull to slightly waxy; Structure: Crystalline, often showing foliation; Cleavage: None (fractures irregularly).
- Hardness
- 6-7 on Mohs scale
- Color
- Gray, black, and white banding/mottling
- Luster
- Dull to slightly waxy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Gray, black, and white banding/mottling; Luster: Dull to slightly waxy; Structure: Crystalline, often showing foliation; Cleavage: None (fractures irregularly).
Formation & geological history
Formed through the regional metamorphism of pre-existing igneous or sedimentary rocks under high pressure and temperature. The rounded shape indicates significant transport and erosion in a fluvial (river) environment.
Uses & applications
Commonly used as decorative landscaping stone, in construction aggregates, or as tumbled stones for hobbyist collections.
Geological facts
River pebbles are natural time capsules; their rounded shape can tell geologists how far the rock traveled from its original source based on its degree of smoothness.
Field identification & locations
Identify by its smooth, water-worn exterior and metamorphic banding. Commonly found in riverbeds, glacial deposits, and coastal beaches.
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