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GIA was kind enough to forward query to the authors of the paper linked in the OP above. Their comments on the (1) Red UV flouresence and the (2) nacreous surface appearance of Windowpane Pearls were solicited. To summarize: 1) That porphyrin is assumed to be the source of the red UV...

Beautiful! Lots of flame in a variety of permutations. Plenty of color. Diamonds and platinum allow the pearls to individually express. A treasure!

Impressive notetaking! Thoroughly enjoyed!

Can't wait!

Attaching detailed studies of Placuna Placenta: 2012 on the microstructural and optical qualities of the shell and 2022 on comparative genetics. Somewhere in this forest of data one would hope something pertaining to this species' red UV shell flourescence might be found. The SEM images do...

Nothing at all on the internet to confirm porphyrin pigment in Placuna Placenta. But at just 1% organic shell composition it wouldn't be much.

Here's the text formatted into a pdf document. Pretty good now on keshi, though it is strange to include Soufflé's as a 'pearl byproduct' when they are produced 100% by design.

Just seeing this. The GIA report linked above does include images of Placuna pearls as well as shells under UV.

Just as Michelangelo "found" David in a block of marble.

CIBJO has been tasked! "Genuine SS Shell Pearl" reminds me of a souvenir stand when exiting the Ephesus ruins in Turkey a couple years ago, marquis stating "AUTHENTIC FAKE WATCHES." Apparently it was effective.

Just to be clear, this conversation has morphed from FW vs. SW to 'pearl' vs. 'shell pearl.' CIBJO (World Jewellry Confederation / Confédération Internationale de la Bijouterie, Joaillerie, Orfèvrerie des Diamants, Perles et Pierres) in its Pearl Blue Book purports to regulate every possible...

That is promising and perhaps a useful umbrella clause, but the descriptions apply to filled mabes, with no specific mention of a spherical NACREOUS 'shell pearl.' In all my years here, this is a new one. I do not visit eBay. (Admission of ignorance, as a plea for enlightenment.) Edit: In...

In reviewing the updated CIBJO Pearl Book (Nov 2024) I am not seeing this term addressed specifically under 'imitations of pearls', particiularly regarding ground and shaped shell nacre. This CIBJO update is enormous, obviously with Jeremy's significant contribution, with a lot of new material...

Nonetheless, unless there is a notable flaw on the backside it's an unusually symmetrical keshi. One must assume keshi considering the pearl's designated fate. But a CT analysis of the pearl in its acrylic tomb would be interesting!

Send the pearls to GIA. But if you have a buyer without need for a certificate, then save your money.

18th century for example. For a true miracle, look to that woman from Herculaneum who preserved a pearl brooch from antiquity in her petrified bosom. No provenance problems there, although a Strontium measurement (SW vs. FW) would be of intetest. Raj it seems you've had a lot of fun developing...

Raj, There is no substitute for certification by a reputable gem lab. Please let us know the results.

Appears to be an unusually elongated and attractive South Seas (P. Maxima) drop. Also appears unlikely to contain a bead nucleus. Do you have any more details from that auction catalogue?

For pearls with a shiny/iridescent surface (commonly known as 'nacre'), there is no way to be sure of natural origin except through detailed analysis and certification by a gem lab specialized in pearls. In any case, such pearls cannot be faked through carving of shell. For pearls with a...

It is most likely carved from shell. If it is a pearl it is a garden variety clam species, without aesthetic merit. I amend my earlier advice, even if it proved to be a pearl—in this case natural as there is no such thing as cultured clam pearls—its value would not justify the lab report expense.