metamorphic
River Pebble (Gneiss/Schist mix)
Metamorphic rock aggregate
Hardness: 6-7 (Mohs); Color: Mottled grey, tan, and dark brown; Luster: Dull to slightly earthy; Structure: Foliated or granoblastic texture; Cleavage: None visible in pebble form.
- Hardness
- 6-7 (Mohs)
- Color
- Mottled grey, tan, and dark brown
- Luster
- Dull to slightly earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Mottled grey, tan, and dark brown; Luster: Dull to slightly earthy; Structure: Foliated or granoblastic texture; Cleavage: None visible in pebble form.
Formation & geological history
Formed through the regional metamorphism of pre-existing igneous or sedimentary rocks under high pressure and temperature. The rounded shape is the result of fluvial erosion (water transport in a river or stream).
Uses & applications
Primarily used as aggregate in construction, road base, landscaping, or as garden decoration. As a common pebble, it has minimal industrial or jewelry value.
Geological facts
The rounded shape indicates a long journey from its source, where tumbling in water smoothed its sharp edges. These rocks can be hundreds of millions of years old, surviving multiple cycles of erosion.
Field identification & locations
Identify by its rounded, smooth surface and mottled, multi-mineral appearance. Commonly found in riverbeds, glacial deposits, and beaches globally.
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