Internal Mold of a Gastropod (Steinkern)
Incomplete specimen; identification to species level is not possible without external shell details (cf. Naticiform or Globular gastropod) • Body fossil (Internal Mold); Invertebrate Mollusk
Geological Period
Uncertain; possibly Jurassic to Cretaceous based on common morphology
Estimated Age
Approx. 66 to 160 million years
Preservation Type
Steinkern (Internal Mold). The original aragonite shell has dissolved or worn away, leaving behind the hardened sediment that filled the cavity.
Condition Assessment
Fair; the specimen is an incomplete weathered internal mold lacking the apex and most diagnostic shell features.
Taxonomic Classification
Phylum: Mollusca, Class: Gastropoda, Order: Uncertain, Genus/Species: Indeterminate
Morphological Description
Specimen exhibits a globular or sub-spherical form consistent with a gastropod whorl. A distinct spiral suture line is visible where the sediment filled the interior of the shell. Surface is smooth to slightly granular, representing the inner casting of the whorl.
Rock Matrix
Fine-grained sedimentary matrix, likely a calcarenite or silty limestone with secondary iron oxide staining giving it a pinkish-tan hue.
Formation & Location
Commonly found in marine sedimentary layers worldwide, such as the chalk or limestone formations of Western Europe or North America.
Size & Dimensions
Approximately 2-3 cm in diameter; consistent with many common Mesozoic marine snails.
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $30 USD (usually bundled in larger lots)
Rarity Assessment
Common; internal molds of gastropods are among the most frequently found invertebrate fossils in marine deposits.
Scientific Significance
Limited. While it indicates a paleo-marine environment, the lack of stratigraphic context and external shell morphology limits its use for biostratigraphy or evolutionary study.
Preparation Recommendations
No further mechanical preparation suggested. Clean with a soft dry brush. Keep in a low-humidity environment to prevent oxidative damage to any trace iron minerals.
Notable Features
Features a distinct suture line and a pinkish mineral tint likely caused by trace amounts of hematite or limonite during the fossilization process.