metamorphic
River Pebble (Quartzite/Siltstone)
Quartzite or Metasiltstone
Hardness: 6.5-7 (Mohs scale), Color: Dull gray-brown, Luster: Matte to waxy, Structure: Fine-grained and dense, Cleavage: None/Conchoidal fracture, Shape: Ellipsoidal water-worn pebble.
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Dull gray-brown, Luster: Matte to waxy, Structure: Fine-grained and dense, Cleavage: None/Conchoidal fracture, Shape: Ellipsoidal water-worn pebble.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone or siltstone under heat and pressure. The ellipsoidal shape is the result of long-term fluvial erosion in a river or coastal environment, where water action has smoothed all sharp edges.
Uses & applications
Commonly used as decorative landscaping stone, in construction aggregates, or as pocket stones/worry stones. Large quantities are used in the production of concrete.
Geological facts
The smooth, rounded shape of river rocks is a perfect example of physical weathering through abrasion. These stones can travel hundreds of miles from their mountain source to reach the sea, becoming smoother and rounder along the way.
Field identification & locations
Identify in the field by its smooth, water-worn texture and lack of visible crystals. Commonly found in riverbeds, stream channels, and ancient glacial deposits. It will not react with acid like limestone would.
