Fossilized Ammonite Shell of the Cretaceous Cleoniceras Cleoniceras Ammonite Shell - Red Iridescent - Height: 201 mm - Width: 168 mm- 1800 g - (1)

Spectacular section polished with ruby opalescence — This specimen represents a carefully polished cross-section of a fossil shell of *Cleoniceras sp.*, an extinct genus of ammonoid cephalopod that lived during the Cretaceous period, about 145–66 million years ago. The preparation reveals the shell's complex internal structure, featuring a central spiraled coil and a large external living chamber, typical of the morphology of these ancient marine creatures. The inner matrix of the shell has been entirely replaced by minerals, a process known as permineralization, which has preserved the finest details of the sutures and the septa. The polished surface of this fossil exhibits an earthy color palette, ranging from light beige to honey-brown, with smoky gray tones and darker accents outlining the ancient chambers. The luster is enhanced by the mirror finish, which captures and reflects light. A distinctive area of iridescence, with hues ranging from fire red to vivid orange, emerges in one of the internal chambers, visible especially under direct light. This phenomenon is due to the presence of fossil nacre or secondary mineralogical alterations that have created an optical light-diffraction effect, giving the specimen an exceptional and rare visual quality. The provenance of this *Cleoniceras* is Madagascar, an island globally renowned for the extraordinary preservation and aesthetic beauty of its ammonite fossils. The Madagascan Cretaceous deposits are famous for yielding specimens that often show exceptional internal mineralization and, in some cases, opalescence or iridescence phenomena. This marine geological deposition context, followed by a slow diagenesis process, has enabled the formation of fossils of such quality and integrity, making them highly desirable for scientific and amateur collection. The structural integrity of the specimen is notable, though natural fracture lines and intrinsic color variations inherent to the fossilization process can be observed, attesting to its authenticity and geological history. The form has been preserved with precision that allows detailed study of its evolution and morphological characteristics. The overall appearance is of great visual impact, highlighting the contrast between the shell's neutral tones and the explosion of iridescent color, making it a display piece. This iridescent *Cleoniceras* is not just a piece of natural history, but also a work of art created by nature, capturing the essence of prehistoric marine life. Its rarity, arising from the combination of significant size and vivid iridescence, makes it a valuable addition to any high-level paleontological collection. It is a fascinating object of study and a highly prized decorative element, capable of stimulating scientific curiosity and aesthetic appreciation for the wonders of our planet's geological past.