uncut Ammonite with rainbow flash, natural aperature, & exposed suture; Madagascar

Ammonites are fossilized cephalopod; extinct marine animals that lived in shells during the Early Cretaceous period, roughly 110 million years ago.

These Cleoniceras; coil-shelled, many-tentacled mollusks disappeared after the dinosaur-killing asteroid strike, in one of the worst mass extinctions of all time.

This ammonite is mostly still in its chambered shell; that shell has built up micro-layers of nacre (aragonite), and when light hits the stacked crystalline aragonite plates, it refracts and produces brilliant flashes of colour. The spacing and thickness of the layers dictate which colors you see. This piece has beautiful rainbow flash.

In some areas the shell was removed and you can see squiggles- those are the suture lines. The lines represent the structural walls (septa) that divided the  growing creature’s shell into individual chambers.

Also, this fossil has had the aperature preserved- thats the branched part at the end of the coil where the tentacles would have extended from.

Interesting factoid:
It is believed that the original discus used by the ancient Greeks in their Olympics was a fossilized ammonite.

From the Mahajanga region of Madagascar. Has been stabilized with resin to protect the fragile outer shell.

Measures roughly 3.5” x 2.5”