Sedimentary or Metamorphic
Unidentified River Rock or Mudstone
N/A (Generic rock fragment)
Small, worn, grey/brownish, opaque, dull to slightly waxy luster, smooth surface due to tumbling or weathering, possible layering or banding.
Identified More sedimentary or metamorphic →
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Physical properties
Small, worn, grey/brownish, opaque, dull to slightly waxy luster, smooth surface due to tumbling or weathering, possible layering or banding.
Formation & geological history
Likely formed from consolidated mud or silt (mudstone/siltstone) or low-grade metamorphism (slate/phyllite). Rounded shape indicates transport by water (e.g., river or beach environment).
Uses & applications
Landscaping, aggregate, decorative filler, or casual collecting.
Geological facts
River rocks are common finds and represent a variety of rock types that have been weathered and smoothed by moving water and friction with other rocks over time.
Field identification & locations
Identified by its smooth, rounded edges and lack of distinct crystal structure. Commonly found in riverbeds, lakeshores, or beaches. Tips for collectors: Check for unique banding, fossils, or hardness testing to narrow down the exact rock type.
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