Provenance
Where a pearl or stone came from. It can multiply the price, and it is the hardest claim to verify.
Origin matters commercially: Kashmir sapphire, Burmese ruby, Colombian emerald and Japanese Akoya all carry a premium over identical-looking material from elsewhere.
For pearls, provenance also carries information rather than just prestige, since it implies the species, the farming method and the likely nacre thickness.
Only a handful of laboratories will state origin at all, because it rests on trace-element analysis and inclusion patterns rather than paperwork.
When you are buying
Treat an origin claim without a laboratory report as a description of style, not of source. It is the single easiest thing for a seller to assert and the hardest for a buyer to check.
Certification Labs
Independent gemmological laboratories that identify and grade stones and pearls. The name on the report is what gives it weight.
X-Ray Testing
The only reliable way to tell a natural pearl from a cultured one, by imaging what is inside it.
Akoya Pearl
The classic small round white saltwater pearl from Japan and China, usually 5mm to 9mm. The pearl in a traditional single-strand necklace.
South Sea Pearl
The largest commercially grown pearl, from the gold-lipped or silver-lipped oyster. Typically 9mm to 16mm, white to deep gold.
Basra Pearl
Natural pearls historically fished from the Persian Gulf. The name is now used far more often than the pearls exist.