Pearl fluorescence, every kind.

[parfaitelumiere]

Hello I am starting a thread about pearl fluorescence.
I have read about specific red color of Cortez sea pearls, glowing red under UV.
Does anyone know how fluorescent are all common pearl species and maybe know more about all wild pearl species?
I will share pictures of my own pearls, known and unknown.

 

[CortezPearls]

It's a great idea
Let me share some of the photos I have, but this thread definitively has to begin with a video, because this visual effect is dynamic, it can be seen more easily with our eyes than with a photograph.

This is a video I made some years ago, that includes Cortez, Freshwater, SSP, Akoya, FWP and Tahitian pearls.

 

[at91]

I've recently started looking into pearls (having spent years collecting gem and mineral specimens). UV fluorescence is one of the tools I use to identify gem characteristics. Since I quite like unheated, untreated gems I've learned a lot about treatments and how to detect them. I was wondering how useful UV characteristics would be to various pearls and the above video is helpful.

I ran across this article, which has quite a bit of information on the topic:

https://www.gia.edu/gems-gemology/s...ightening-in-chinese-freshwater-edison-pearls

I found this article fascinating on a number of levels. Looking at the illustrations from the article, particularly Figs. 2 & 3 and the Results table, a number of interesting details are revealed:

1) It suggests LWUV is a very good method of determining brightening/bleaching/maeshori treatments in some pearls. I was interested to learn that some, but not all, "natural" color freshwater pearls are subjected to brightening/bleaching. I know Akoya often are brightened, hence the term "maeshori". I gather this is not particularly likely to affect the value of high quality pearls, but as a consumer I do like to know what is completely natural versus treated in any way.

2) I found it highly interesting that the definitely color treated CFWP "Edison" pearls were in colors of golden, deep/strong blue, and strong purple. With the golden ones (which could be mistaken for SSP at first glance) it would appear LWUV might be able to sort them as they have a different glow under LWUV than other pearls.

3) I found it useful to know that many "natural" pastel-colored CFWP, even ones with very strong orient, do not appear to be treated in any way.

4) Slightly off topic, but I found it interesting that Grace Company sent GIA several Edison pearls that turned out to have no nucleus but otherwise appeared to be very round and outwardly like bead-nucleated Edisons. It was also interesting that all of the non-bead cultured pearls submitted were all smaller than 9mm and GIA attributed it to the mussel rejecting the bead. I assume it would be difficult to grown very round CFWP in sizes larger than 9mm without bead nucleation. Thoughts?

My ultimate takeaways: CFWP with strong colors of yellow, blue and purple are probably color treated; lighter colors of CFWP might be brightened/bleached. LWUV is a good sorting tool for some types of pearls.

Here's my own personal test with a short strand of 10mm bead-cultured "Edison" pearls using a strong LWUV (390nm UV-A) flashlight:

 

[at91]

Here is a comparison of vintage Akoya pearls to recent CFWP "Edisons". It's hard to capture with a photo, but the Akoyas definitely have that LWUV glow, unlike the CFWP where even the very light ones in this strand do not glow.

 

[CortezPearls]

Hello at91 and welcome to our forum!
Sorry it took me so long to moderate your post we had an internet outage in the area from midday to midnight! Yikes!
Thank you for sharing that G&G article...I was actually going over the UV testing and found it very interesting as well. I love UV testing.

And the photos you have posted are good!
I prefer to use a black (cloth) background for UV tests since the UV light can actually bounce off the light backgrounds and hurts your eyesight.

In my experience: artificially colored pearls do not display fluorescence. Of course, black pearls do not show off any as well.
But I do wish I could have time to test larger numbers of pearls, especially FWPs, groups that are guaranteed to be dyed and untreated and in all assorted colors. Just like melanin in black pearls, there could be something (pigments, carotenoids?) in some kinds of pearls that could affect UV fluorescence...but I would really like to read more and see more.