Madagascar Ammonite Fossil – 29 g (45 × 12 × 39 mm)

This 29 g ammonite fossil originates from Madagascar.
It displays a classic spiral shell structure with clearly defined internal chambers, now mineralised with translucent calcite and subtle smoky quartz tones. The surface is polished, revealing intricate suture lines and a warm palette of beige, caramel, and grey.
Dimensions: 45 × 12 × 39 mm.
AGE
Formed during the Late Jurassic to Early Cretaceous, approximately 160–100 million years ago, when ammonites thrived in warm marine environments before their extinction at the end of the Cretaceous.
Formed during this extended geological history, the piece is valued for its scientific clarity, aesthetic symmetry, and insight into ancient marine ecosystems.
Technical notes
• Hardness: ~3–4 (calcite infill)
• Luster/Finish: Polished, vitreous to waxy
• Transparency/Preservation: Translucent chamber infill with opaque shell walls
• Fossil type: Ammonite (extinct marine mollusk, subclass Ammonoidea)
• Crystal habit / Morphology: Planispiral shell with chambered internal structure
• Associations / Matrix: Calcite, quartz, fossil shell material
• Composition / Formation: Fossilisation via mineral replacement and infill of shell chambers
• Fluorescence: None expected
This piece is polished to reveal its internal structure, making it suitable for display, study, or collection.