Oyster Shell Fragment / Gryphaea or Exogyra related bivalve
Exogyra cf. virgula or Gryphaea sp. • Body fossil, invertebrate bivalve mollusk
Geological Period
Jurassic to Cretaceous (specifically Callovian to Oxfordian, given the Vaches Noires context)
Estimated Age
160 to 165 million years old
Preservation Type
Original calcitic shell material preserved with minor secondary recrystallization and matrix infilling
Condition Assessment
Fair to Good; weathered fragment showing partial breakage and worn margins typical of wave-washed coastal finds
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia, Order: Ostreida, Family: Ostreidae
Morphological Description
Irregular bivalve shell fragment showing strong foliated calcite structures, alternating dark grey and white mottled patterns, irregular concentric growth lamellae, and attachment area indicating cementation to a hard substrate.
Rock Matrix
Argillaceous limestone / marl characteristic of the coastal cliffs of Normandy
Formation & Location
Falaises des Vaches Noires, between Villers-sur-Mer and Houlgate, Normandy, France
Size & Dimensions
Approximately 35 mm to 40 mm in maximum length, comparable to a standard 2-euro coin shown for scale (25.75 mm diameter)
Value & Rarity
Estimated Market Value
5 to 15 USD
Auction Estimate
10 to 25 USD
Rarity Assessment
Common
Scientific Significance
Demonstrates shallow marine benthic environments of the Jurassic sea that covered northern France, providing insights into oyster paleoecology and substrate attachment strategies
Preparation Recommendations
Gentle washing with water and a soft brush to remove residual clay; no aggressive chemical preparation required; store in a dry ambient environment
Notable Features
High-contrast natural coloration between the dark grey micritic/clay-rich inclusions and the bright white calcitic shell layers, giving it an aesthetically pleasing mottled appearance
Notes
falaises des Vaches Noires