Auction Rings

I purchased several rings at auction, advertised as turquoise. I am a complete newbie so I didn’t realize that these could be fake until beginning my research. I would very much appreciate some help. After looking around a bit I am fairly sure that I don’t have any natural turquoise here. :confused:

Everything looks like real turquoise, most of them will be stabilized. The only thing that looks like it is imitation is the ring between the purple spiny oyster shell/turquoise cluster ring and the single turquoise stone ring with three drops on the left. Stabilized turquoise is real turquoise, just something that has been helped to darken and make the stone harder.

Jason, Thank you so much for your response!!