Belemite Rostrum (Thunderbolt)
Belemnitella cf. americana • Body fossil, Invertebrate Cephalopod
Geological Period
Cretaceous (Late Cretaceous)
Estimated Age
66 to 100 million years
Preservation Type
Recrystallization of calcite (original shell material replaced or reorganized during lithification)
Condition Assessment
Fair to Good; the specimen is worn with some surface erosion and is missing the very tip and the complete alveolar section.
Taxonomic Classification
Phylum: Mollusca, Class: Cephalopoda, Order: Belemnitida, Family: Belemnitellidae, Genus: Belemnitella
Morphological Description
A calacareous bullet-shaped internal shell (rostrum). Features a tapered, conical body with a hollowed-out alveolar end (partially visible or broken) and a rounded/pointed apex. The surface shows some fibrous calcite structure and longitudinal vascular imprints typical of the family.
Rock Matrix
Minimal remaining; appears to have been weathered out of a soft chalk or marl matrix, typical of marine sediments.
Formation & Location
Likely Mount Laurel Formation (New Jersey, USA) or similar Cretaceous chalk deposits in Europe (UK, France, Netherlands).
Size & Dimensions
Approximately 3.5 to 4 cm in length; typical for individual rostrum segments within the genus Belemnitella.
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $20 USD (usually sold in small lots rather than individually)
Rarity Assessment
Common; found in great abundance in specific Cretaceous strata worldwide.
Scientific Significance
Belemnites are important index fossils used for biostratigraphy. They provide insights into Mesozoic marine food webs as they were a primary food source for marine reptiles and sharks.
Preparation Recommendations
Mechanical cleaning with a soft brush; stabilize any deep cracks with a thin paraloid B-72 solution if needed. Store in a dry environment to prevent surface degradation.
Notable Features
Shows classic concentric growth rings when viewed in cross-section at the broken end and characteristic brown/amber coloration from calcite replacement.