Agree with
@BWeaves they are Chinese FW pearls, most likely dyed. The "potato shape" is a dead give away.
Unfortunately the GIA evaluations they use at EBay is not the same as sending items to GIA for actual evaluation. Pearls sent to GIA are VERY expensive to evaluate...and they will actually X-Ray the pearl to determine the nacre thickness, as well as lots of other information. How much did you pay for these? And, did the seller offer a "refund?"
Tahitians should look more like this: Round to near-round with the classic "fishbite" markings. Some Tahitians are perfect with no markings, but those pearls are much, much more expensive. I did swap out the clasp, but the quality of the clasp on any strand can often be a good indication of the strand's value.
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Here is a mixed color "Tahitian" strand...again, also near round with similar markings.
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