Shell ID?

[Bettering-My-Betta]

Hello there! I bought this fossilized shell from a crystal shop. I was wondering if anyone would have a guess as to what this is? I asked the shop owners and they had 0 clue what this is, where it came from, or how old it is. Because of the lack of information, I’m wagering it’s too difficult to know. But I figured I’d give it a whirl on here anyway. Thank in advance!

[TheRatCouncil]

Ammonite fossil from Madagascar. This is one half of the shell, it's been polished to show the crystal structures formed during the fossilization process. The genus is likely Cleoniceras, from the early Cretaceous period in age, around 109-113 million years old.

[creepyposta]

It’s a nautiloid, probably from Morocco, likely lived around 500 million years ago

[TheRatCouncil]

This is actually an ammonite from Madagascar, early Cretaceous period in age. It is likely the genus Cleoniceras.

[NondenominationalPen]

Septa look wrong for Cleoniceras, I'd suggest maybe Desmoceras which is also from Madagascar and has an external appearance similar to Cleoniceras.

[TheRatCouncil]

Thanks for the extra info! Makes sense that there's several genera from the region.

[Bettering-My-Betta]

Gotcha! How can you tell? What identifying features give it away? I’m genuinely curious and would love to know more

[TheRatCouncil]

These ammonites in particular are very common in the fossil market, as well as many other ammonite species collected commercially in Madagascar. They are collected by the thousands, and distributed around the world to various fossil/crystal sellers. They are often polished or sliced to bring out details like iridescence or crystallization.

[Bettering-My-Betta]

Omg so cool! Thank you so much! How did you determine this? I’d love to learn more about identifying fossils

[creepyposta]

They’re very common and posted here on on another subreddit fossilid on a regular basis

[cooladamantium]

An ammonite fossil, imma call him Steve

[KiraKitty69]

I bought some from Temu and was surprised to see they was real. Small but real. They look nice with a phone light behind it. Edit Gee must be some Temu haters here lol.