sedimentary
Fossiliferous Mudstone / River Pebble
Sedimentary rock with trace fossil or inclusion
Hardness 3-5, dull to earthy luster, gray to tan color with darker fine-grained inclusions, smooth river-worn texture, irregular fracture
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Physical properties
Hardness 3-5, dull to earthy luster, gray to tan color with darker fine-grained inclusions, smooth river-worn texture, irregular fracture
Formation & geological history
Formed through the accumulation, compaction, and cementation of fine-grained silts, clays, or mud in ancient aquatic environments such as riverbeds or lakes. Subsequent erosion tumbled the rock into a rounded river pebble.
Uses & applications
Commonly used as decorative garden stone, landscape gravel, or collected as a casual natural specimen.
Geological facts
River pebbles often preserve ancient sedimentary features or small fossilized impressions embedded within the fine silt matrix before it hardened over millions of years.
Field identification & locations
Identified in the field by its smooth, water-rounded shape and micro-crystalline earthy texture. Frequently found along riverbanks, beaches, and glacial gravel deposits.
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