Sea Snail Internal Mold (Steinkern)
Gastropoda indet. (Internal Mold) • Internal Mold (Body Fossil), Invertebrate Gastropod
Geological Period
Cretaceous to Paleogene (likely)
Estimated Age
Approximately 50 - 100 million years
Preservation Type
Internal mold (steinkern) with secondary mineral replacement. The internal cavity was filled with sediment that lithified, while the outer shell dissolved over time.
Condition Assessment
Poor to Fair. The specimen is highly weathered, lacks diagnostic surface ornamentation from the original shell, and is incomplete.
Taxonomic Classification
Phylum: Mollusca, Class: Gastropoda, Order: Unidentifiable, Family: Unidentifiable
Morphological Description
Dark, irregular nodular shape with visible recrystallized mineral pockets. The specimen lacks its original shell material but exhibits a slight spiral or coiled volume characteristic of a gastropod's internal cavity. Surface is pitted and heavily weathered.
Rock Matrix
Minimal remaining matrix; appears to be composed of iron-rich or phosphatic mineralized sediment with small quartz or calcite inclusions.
Formation & Location
Commonly found in coastal formations such as the Monmouth Formation (New Jersey, USA) or the Hornerstown Formation, which are known for producing darkened, mineralized marine fossils.
Size & Dimensions
Small specimen, approximately 1.5 cm - 2.5 cm in length; typical for common small marine snails.
Value & Rarity
Estimated Market Value
$1 - $5 USD
Auction Estimate
N/A (Typically sold in bulk lots for educational purposes)
Rarity Assessment
Common. Internal molds of gastropods are among the most frequently found marine fossils in sedimentary deposits.
Scientific Significance
Low. While it confirms the presence of gastropods in a specific paleoenvironment, the lack of preservation of the outer shell makes taxonomic identification and paleoecological analysis difficult.
Preparation Recommendations
Keep dry in a plastic display case. No chemical cleaning is recommended as the specimen is stable but fragile to mechanical abrasion.
Notable Features
The most notable feature is the high degree of mineralization and the crystalline pockets visible on the surface, indicating secondary mineral growth within the mold.