Opalized Ammontes

[ezajac]

Hi all,

 

Recently saw an opalized ammonite out at a rock and fossil shop in Colorado. It was really quite beautiful but as I'm pretty much an amateur when it comes to identifying fossils, I have concerns about its authenticity. I'm wondering if anyone can give tips on how to spot fakes.

 

thank you! 

[sdsnl]

Do you mean the ammonite has iridescent colors? That would be nacre not opal (though many sellers call them opalized). They are common in Madagascar and would be nice to have if you like them for the look and as a fossil. Don't buy if you are interested in it for the "opal".

[jpc]

There are very few opalized ammonites.  I agree with what sdnl says...it is most likely well preserved nacre, which is pretty common in local ammonites out here as well.