I purchased this ring and I was told it was 100% natural Irani Turquoise. It looks like an Irani Turqoise. i did rub a qtip with acetone and no color come off. But I did a hot knife test and it burned the stone and it gave a plastic smell.
Mystery, turquoise stones can have other properties in them. Matrix (host rock), quartz, pyrite are some of the more common, those could be the culprit. Could also be the stabilization.