Marine Shell Fragment (likely Bivalve or Gastropod)
Indeterminate marine mollusk cf. Gryphaea or Crassostrea fragment • Body fossil fragment, invertebrate macrofossil
Geological Period
Cretaceous to Neogene (likely Neogene/Quaternary)
Estimated Age
2 to 100 million years
Preservation Type
Recrystallization and mineralization; heavily abraded by water action
Condition Assessment
Poor to Fair; significant weathering, lack of diagnostic margins, and partial completeness
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia or Gastropoda
Morphological Description
A weathered, calcified fragment showing a thickened umbonal region or hinge area. Surface is smooth from water-worn abrasion with some internal layering visible in cross-section. Dark gray to brownish secondary mineralization is present.
Rock Matrix
None; specimen is free-matrix, likely a beach-find or stream-washed pebble
Formation & Location
Commonly found in coastal Cenozoic formations (e.g., Calvert Formation, USA) or beach lag deposits worldwide
Size & Dimensions
Approximately 2-3 cm; small fragmentary state relative to a whole adult shell
Value & Rarity
Estimated Market Value
$1.00 - $5.00
Auction Estimate
N/A (Group lot value only)
Rarity Assessment
Common; found in high abundance in marine fossiliferous deposits
Scientific Significance
Low; common indicator of previous marine environments but lacks specific diagnostic features for stratigraphic dating
Preparation Recommendations
Minimal preparation required; gentle cleaning with water and storage in a dry environment to prevent salt crystallization if found near the ocean
Notable Features
The dark coloration suggests phosphate or manganese enrichment during the fossilization process in a marine reductive environment.