Found in South Dakota

[JTRock]

My first attempt at identification.

I hope the pic sizes are ok.

 

I found this in South Dakota. It was my first attempt at finding fossils.  Either at the Mount Moriah Cemetery in Deadwood or Badlands.

A local expert said it was a shell, possibly ammonite. I'm hoping for a verification. These pics are front and back.
 

ALSO, it feels quite solid but it does have cracks. I was planning to have it made into maybe a necklace for a friend, possibly in a macrame setting. I'd like to make it more solid first. I'd like opinions for how to  do this. I've read many ways and products but the opinions are widely varied.

Thank you for your time.

 

I have two more fossils and will put those in their own posts.

 

Thanks,

Jeff

[Ludwigia]

This does not appear to be a shell, but rather a so-called steinkern of a partial and poorly preserved ammonite. I'd suggest dripping some liquid super glue into the cracks in order to stabilize it.