Tooth test was somewhat gritty.
Also, EBay is great about stepping in and helping with returns, even if a person doesn't offer a return policy. EBay's policy is that returns are required if the item is not "as advertised." So if something is advertised as "Tahitian Pearls" and they turn out to be imitation, then EBay will step in to require a refund. I've only had to call on this help once, but it was great to have EBay behind the the purchase. Most sellers are unfamiliar enough about pearls that they appreciate knowing when something is imitation and willingly return the item.
Once I purchased from a seller who was advertising South Sea when they were just really nice Freshwaters. He was very angry about the return, and blocked me as a purchaser. His jeweler had told him they were South Sea. So, even Jewelers get it wrong. Overall I've had very good experiences purchasing on EBay. Most people selling want to do the right thing-and I'm happy to purchase if it is the "real thing." I do not purchase from China, only Estate and Vintage/Used in the US or Europe. I've found some lovely items at good prices.