Iridescent Xipheroceras Calcite Ammonite Fossil Jurassic Lyme Regis Dorset UK

Description

Authentic Iridescent Xipheroceras Calcite Ammonite from the Jurassic Coast

Offered here is a genuine iridescent Xipheroceras calcite ammonite fossil with a cut base, collected from the classic Black Ven Marls at Stonebarrow Cliff, Charmouth, Lyme Regis, Dorset, on England’s world-famous Jurassic Coast. This carefully chosen specimen exhibits attractive natural iridescence across the shell surface, adding a rare visual quality to an already iconic Lower Jurassic ammonite. The photographs show the exact fossil you will receive, and full sizing details are provided in the photos.

This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card, providing confidence in provenance and long-term collectability.

Geological Formation and Age

This ammonite originates from the Lower Lias Group, deposited during the Early Jurassic Period, approximately 199–191 million years ago, within the Sinemurian Stage. The Black Ven Marls are composed of fine-grained marine mudstones and marls formed in a shallow epicontinental sea that once covered much of southern Britain. Stonebarrow Cliff is one of the most scientifically important Lower Jurassic localities in Europe, renowned for producing ammonites essential to Jurassic stratigraphy and palaeoenvironmental reconstruction.

Fossil Type, Species, and Scientific Context

Xipheroceras is an Early Jurassic ammonite genus belonging to the Order Ammonitida, Superfamily Eoderoceratoidea, and Family Eoderoceratidae. It is a well-documented genus within Lower Lias ammonite assemblages and plays an important role in understanding early ammonite diversification following the end-Triassic extinction. Specimens from the Dorset coast are particularly valued due to their clear stratigraphic context and strong preservation.

Morphology, Iridescence, and Calcite Preservation

This specimen displays the characteristic planispiral coiling of Xipheroceras, with relatively open whorls and distinct ribbing across the flanks. Rib strength and spacing subtly vary through growth, reflecting natural ontogenetic development. The ammonite has undergone calcite mineralisation, enhancing fine shell detail and providing a pale crystalline base colour.

Areas of natural iridescence are visible on the shell surface, created by light interference within thin mineral layers formed during fossilisation. This effect produces shifting colours under different lighting angles and is a highly desirable feature among collectors.

The cut base has been professionally prepared to allow the fossil to stand securely upright, making it ideal for cabinet, shelf, or desk display without additional supports.

Depositional Environment

During the Early Jurassic, the Charmouth and Lyme Regis region lay beneath a warm, shallow marine environment rich in ammonites, belemnites, fish, and marine reptiles. Fine sediments accumulated slowly on the sea floor, allowing ammonite shells to be rapidly buried after death. Periodic low-oxygen conditions reduced scavenging and disturbance, contributing to the exceptional preservation and occasional iridescence seen in ammonites from the Black Ven Marls. These conditions underpin the global significance of the Jurassic Coast fossil record.

Collecting, Display, and Educational Value

This iridescent Xipheroceras calcite ammonite fossil with cut base is ideal for serious fossil collectors, educational collections, museum displays, or refined interior presentation. Its combination of classic British Jurassic provenance, clear taxonomic identification, attractive iridescence, and practical display preparation makes it both scientifically informative and visually striking. Iridescent ammonites from Stonebarrow Cliff are increasingly sought after and comparatively uncommon. Each specimen we offer is individually selected to ensure you receive an authentic and carefully curated piece of Early Jurassic marine history from one of the world’s most important fossil coastlines.