fossil
Fossilized Shell Impression / Siltstone Fossil
Bivalvia / Brachiopoda mold in Siltstone
Hardness: 3 to 6 depending on matrix; Color: Greyish-brown to tan; Luster: Dull, earthy; Texture: Fine-grained with prominent ribbing/grooves from ancient shell impression.
- Hardness
- 3 to 6 depending on matrix
- Color
- Greyish-brown to tan
- Luster
- Dull, earthy
Identified More fossil →
Explore Fossilized Shell Impression / Siltstone Fossil in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3 to 6 depending on matrix; Color: Greyish-brown to tan; Luster: Dull, earthy; Texture: Fine-grained with prominent ribbing/grooves from ancient shell impression.
Formation & geological history
Formed in shallow marine or aquatic sedimentary environments where ancient shelled organisms (like bivalves or brachiopods) were buried in fine silt or mud. Over geological time, the soft tissue decayed and the shell dissolved or was replaced, leaving a casts/molds preserved in sedimentary rock.
Uses & applications
Educational specimens, amateur fossil collecting, and geological study of ancient marine environments.
Geological facts
Fossil molds and casts preserve the external surface morphology of extinct or ancient organisms without retaining the original shell material. They are crucial for dating sedimentary rock layers.
Field identification & locations
Identified by the distinct parallel linear grooves or ribs characteristic of shell ornamentation on a fine-grained sedimentary rock pebble. Frequently found along riverbeds, beaches, and sedimentary rock outcrops globally.
More like this
Other fossil specimens
Crinoid Stem Fossil in Matrix
Phylum Echinodermata, Class Crinoidea
fossil
Sedimentary Outcrop (Sandstone/Shale)
Sedimentary bedrock formation (variable composition)
sedimentary
Chert with Fossil Brachiopod
Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion
sedimentary
Fossilized Crinoid Stem in Limestone
Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix
fossil
Fossiliferous Limestone
Limestone with embedded fossil cross-section
sedimentary
Fossiliferous Limestone
Fossiliferous Calcilutite / Biomicrite
sedimentary