sedimentary
Bivalve Fossil in Sedimentary Matrix
Fossiliferous Mudstone (Class: Bivalvia)
Hardness: 3-5 (matrix varies); Color: Gray, brown, and white; Luster: Dull/earthy matrix with pearly fossil highlights; Crystal Structure: Amorphous/cryptocrystalline; Cleavage: None
- Hardness
- 3-5 (matrix varies)
- Color
- Gray, brown, and white
- Luster
- Dull/earthy matrix with pearly fossil highlights
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Physical properties
Hardness: 3-5 (matrix varies); Color: Gray, brown, and white; Luster: Dull/earthy matrix with pearly fossil highlights; Crystal Structure: Amorphous/cryptocrystalline; Cleavage: None
Formation & geological history
Formed through the lithification of marine or freshwater sediment where shells were buried. The organic shell material is often replaced by minerals like calcite or aragonite over millions of years.
Uses & applications
Scientific research, educational use, and paleontological collecting. Sometimes used as decorative architectural stone if the density of fossils is high (coquina).
Geological facts
The concentric growth lines visible on the shell surface can sometimes be used to estimate the age of the mollusk when it died, similar to tree rings.
Field identification & locations
Look for visible symmetry and growth rings in sedimentary rock layers, particularly shales or limestones. Common in areas that were formerly ancient sea beds.
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