Ammonite Half Fossil Cretaceous Madagascar Polished Genuine Specimen with Certificate of Authenticity

Description

Overview

This beautiful Ammonite Half Fossil from Madagascar is a genuine specimen from the Cretaceous Period, polished to reveal the intricate internal chamber structure that once housed the soft body of an ancient marine cephalopod. Each piece has been expertly cut and polished to expose its natural spiral geometry, showcasing the mineralised aragonite and calcite infillings that formed over millions of years. The specimen shown in the photograph is the exact one you will receive. A 1cm scale cube is included for accurate sizing reference—please see the photo for full measurements.

All of our fossils are 100% genuine and come with a Certificate of Authenticity, ensuring that your purchase is scientifically verified and responsibly sourced.

Geological Background

This specimen originates from the Cretaceous strata of Madagascar, a region world-renowned for its superbly preserved ammonite fossils. During the Cretaceous, approximately 145 to 66 million years ago, the island’s coastal marine environments supported diverse ammonite populations thriving in warm, shallow seas. The fine-grained limestones and marls of these deposits provided perfect conditions for fossilisation, preserving both external shell morphology and internal chamber detail in remarkable clarity.

Over geological time, the original aragonitic shell material was replaced by minerals such as calcite, quartz, and sometimes pyrite, producing the stunning crystalline cross-sections visible in this half fossil. These polished halves reveal the ammonite’s iconic planispiral coiling, with chambers divided by intricate septa forming elegant suture lines—the complex internal partitions that are diagnostic of ammonite families.

Palaeontological Significance

Ammonites belong to the subclass Ammonoidea, within the class Cephalopoda, related to modern squid, cuttlefish, and nautilus. These extinct marine molluscs were active swimmers and formidable predators, using their tentacles to capture prey in open marine waters. The Madagascar specimens, often attributed to genera such as Cleoniceras or Douvilleiceras, are particularly notable for their well-preserved whorls and rich mineralisation, reflecting a high level of diagenetic transformation without loss of fine anatomical detail.

This half fossil elegantly displays the internal structure of the phragmocone—the buoyancy control chamber system used by ammonites to navigate the ancient seas. The visible septal divisions illustrate the evolutionary adaptation that allowed these animals to maintain neutral buoyancy and efficient locomotion.

Aesthetic and Collectible Qualities

Each Madagascan ammonite half is unique, displaying a natural palette of golden browns, silvers, greys, and honey-coloured calcite crystals. The polish enhances both its aesthetic appeal and the visibility of the internal chamber geometry, making it ideal for collectors, educators, and home décor enthusiasts alike. The fossil combines scientific value with natural artistry—an enduring relic of Earth’s prehistoric oceans.

Provenance and Authenticity

This ammonite fossil was sourced ethically from the renowned Mahajanga Basin deposits of Madagascar. The piece has been carefully selected for clarity, preservation, and visual balance. It has been professionally prepared to museum-quality standards, ensuring that the delicate structures are stabilised and beautifully presented.

Your purchase includes a Certificate of Authenticity, verifying the fossil’s geological age, location, and species classification. Each fossil is hand-selected to represent the finest natural history specimens available on the market.

Summary

This Cretaceous Ammonite Half from Madagascar offers an extraordinary window into the ancient marine world. Its detailed preservation, striking mineralisation, and scientifically significant structure make it an exceptional addition to any fossil collection. Whether purchased for study, display, or as a natural conversation piece, this fossil embodies the perfect union of science, history, and beauty—a timeless treasure from the depths of geological time.