X-Ray Testing
The only reliable way to tell a natural pearl from a cultured one, by imaging what is inside it.
An X-ray shows the pearl's internal growth structure. A natural pearl has concentric rings all the way to the centre; a bead-nucleated pearl shows a solid core with a distinct boundary.
Tissue-nucleated freshwater pearls have no bead, so they are read on the pattern of their growth rings and voids instead.
It is non-destructive, which is why laboratories can test a strung necklace without taking it apart.
When you are buying
Any claim that a pearl is natural or Basra is unverifiable without this test. If a seller will not send a piece to a laboratory before a high-value sale, treat the claim as marketing.
Natural Pearl
A pearl that formed with no human involvement at all. Vanishingly rare, and effectively absent from the retail market.
Basra Pearl
Natural pearls historically fished from the Persian Gulf. The name is now used far more often than the pearls exist.
Bead Nucleated
Grown around a round shell bead, so the pearl is a nacre shell over a core. The saltwater method, and how roundness is achieved.
Certification Labs
Independent gemmological laboratories that identify and grade stones and pearls. The name on the report is what gives it weight.
XRF Testing
A non-destructive X-ray test that reads metal purity in seconds. What the karat meter in a jeweller's shop actually is.