On eBay even 100% positive feedback is no guarantee of a credible seller.
This seller has only 99.8%, including 7 neutrals, one negative and a couple of false positives.
Most complaints are about over-described stones.
When buying, remember that return shipping with confirmation of delivery is a necessity for refunds on items that are Not As Described.
And shipping internationally with tracking is very expensive.
While feedback is voluntary and only about 40% of transactions get any feedback, there is enough of a pattern to the complaints to make a sophisticated online buyer wary.