Crystalline Fossilized Shell Fragment or Mineral Pseudomorph
Incomplete specimen prohibits specific identification; cf. Inoceramus fragment or large bivalve • Body fossil / Replacement fossil; Invertebrate (likely Molluscan origin)
Geological Period
Potentially Cretaceous to Neogene
Estimated Age
5 to 100 million years
Preservation Type
Recrystallization / Replacement; calcite or aragonite mineralization replacing original organic shell structure
Condition Assessment
Fair; the specimen is a fragmentary section and not a complete organism. It shows signs of mechanical weathering and breakage on the edges.
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia (uncertain), Genus: indeterminate
Morphological Description
Elongated, plate-like structure with visible parallel growth lines or ribbing. The texture is overtly crystalline, consisting of elongated prismatic crystals oriented perpendicular to the shell surface.
Rock Matrix
Minor adhering grey limestone or silty mudstone matrix; high carbonate content
Formation & Location
Commonly found in marine limestone formations such as the Pierre Shale (USA), the Chalk Group (UK/Europe), or various Tertiary marine deposits
Size & Dimensions
Approximately 12-15 cm in length; consistent with large-bodied extinct shellfish
Value & Rarity
Estimated Market Value
$10.00 - $35.00 USD
Auction Estimate
$20.00 - $50.00 USD (typically sold in bulk lots)
Rarity Assessment
Common; crystalline shell fragments are abundant in many marine fossil-bearing strata globally.
Scientific Significance
Provides evidence of local paleo-environmental conditions and post-depositional mineral replacement processes in marine benthic ecosystems.
Preparation Recommendations
Mechanical cleaning with a soft brush; avoid acidic cleaners as they will dissolve the carbonate structure. Keep in a low-humidity environment.
Notable Features
Highly pronounced prismatic crystal structure that mimics the original biological architecture of the shell wall.