Candeling of very old, supposedly cultured pearls

[Conny Forsberg]

Hi you all,
from a pearl "amateur". Though I'm a gemologist, diamond grader and precision cutter since more than 30 years pearls are not really my field of expertise. I love pearls and enjoy wearing my Tahiti pearl. The ones I consider primarily wearable by men as well as women.

On to the topic of the post. I bought a very old string of pearls with a 18K diamond set gold clasp and attached extra security chain. Also 18K. Pearls are from semi round to baroque in shape. Seeems the nacre layer is very thick. I have shot some images when candeling. Anyone like to chime in and tell me what we are looking at?





I have quite a few more but lets start with these.

Cheers,
Conny

 

[KAC]

can you post pictures of the pearls in everyday light?

 

[Conny Forsberg]

Absolutely, here comes a couple of quick shots under daylight lamp.
The pearls are pretty dirty close to the silk and drill holes, sorry for that...

 

[pattye]

Welcome, Conny, this is a most interesting necklace! Approx what size are the pearls? I can see that they need a bath and restringing. When you look at the pearls near the thread, is there areas where the nucleus is exposed? (like that pearl with the large dark area on the right in the photo above.) When you have the pearls off the string, you may be able to estimate nacre thickness by peering down the drill hole with a loupe. We'd love to see the clasp & safety also. It might help to date the pearls.

 

[Conny Forsberg]

The answer is that I have not been able to see any nucleus through the drill holes. Usually one can see the borderline very easily in nucleated cultured pearls when drilled. That is why I guess the nacre is pretty thick.

Conny

 

[Lagoon Island Pearls]

Welcome to P-G Conny,

Your image is well composed and critically focused. However, if possible, I'd like to see other views of the same pearl on one or more axis that I may envision a three dimensional view. Likewise (again if possible) other views of additional pearls in the strand, but not necessarily from all axis.

I have some thoughts, but will comment once I've seen other images. I'm also intrigued to follow your post on Raman spectrometry.

 

[Conny Forsberg]

Thanks Dave and Patricia.
Sizes of pearls are from approximately 3 mm to 7.5/8.0 mm
Here comes a first series of images. Same pearl different views.

 

[Conny Forsberg]

Another set...

 

[Conny Forsberg]

Yet another...

 

[Lagoon Island Pearls]

Nice imagery, Conny!

Firstly, many thanks for the open-minded inquiry. It's refreshing to observe candled views of pearls without the expectation of deeming them as natural.

When reading candled views, I look for a few things. Namely whether the contrasts are deep or near the subsurface. In the case of these views, it's largely subsurface. Some have slightly dark contrasts, but not to the degree you'd observe in natural pearls. Natural pearls often have dark, eccentric or randomly oriented steaks, spots and inclusions or in some cases, no visible nuclei at all.

Although some variations are visible, all of the pearls in this lot generally resemble each other internally and externally. Natural pearls are most often be graded by their appearance at the surface, but will have markedly different contrasts at the nuclei. Tissue grafts tend to blend into the pearl with medium graduation. The distal aspect of a graft often appears as two semi translucent spots, being the corners of the section of the donor tissue.

Considering the age of this strand, the clasp and the overall visual appearance, these are likely akoya keshi pearls.

 

[GemGeek]

Humor a fellow gemologist by taking a photo in indirect natural light on a paper towel. And put a pen or pencil in the shot for a visual size reference. Thanks!

 

[Conny Forsberg]

Thanks for your opinion Dave!
Akoya keshi sounds interesting but I'm still not convinced they are not nucleated. Is it not possible they are nucleated and have spent a great deal of time in growth? I will dismantle the necklace and have it restrung anyway as I intend to give it to my youngest daughter. When dismantled and cleaned it will be easier to inspect the drill holes. Will also compare with some pearls bought as SS keshis I have in my collection.

I'll humor your wish GemGeek but I guess I skip the paper towel and use my normal background for gem and jewellry imaging, a 25% grey as above. Why the pencil? I measured the pearls yesterday, 3+ to 7.5/8.0 mm. Pencil it will be though
Hard time finding daylight today as it probably will be dark when I get in to the lab. Will give it a shot during the weekend.

Conny

 

[GemGeek]

Pearl color does best against white, in my opinion.. In your photos under the lamp, the surfaces look like South Sea pearls. A good cleaning will help to reveal their true nature, as will the natural light. Forget the dorky pencil idea. I was thinking to throw in a dime, but realized you would have different currency.

 

[Conny Forsberg]

As I had no daylight to work in when getting to the lab I decided to make some other research...
Here comes a photoluminiscence spectrum comparison between the pearls in the necklace and known south sea keshis. All pearls (6) shot from the necklace has close to identical spectra which pearls from same environments and species of mollusc seem to have. The south sea keshis I own have almost identical spectra too.

 

[Lagoon Island Pearls]

As I had no daylight to work in when getting to the lab I decided to make some other research...
Here comes a photoluminiscence spectrum comparison between the pearls in the necklace and known south sea keshis. All pearls (6) shot from the necklace has close to identical spectra which pearls from same environments and species of mollusc seem to have. The south sea keshis I own have almost identical spectra too.

That is a compelling and convincing comparison.

Initially, I thought SS for the matched silver hue, but "very old" steered me to akoya for practical reasons. Now I'm curious how and where a SS strand of this type reared itself so long ago.

 

[Conny Forsberg]

Sorry, I guess I was unclear above. The pearls in the necklace differs from the SS pearls. All pearls from necklace, tested by spectrometry had the spectra seen as the white line in the image above. All the SS pearls tested had a spectrum matching the violet line. Tahiti pearls had another very different spectrum. Yet another spectrum was seen in a Tridachna pearl. I will sample as many types of pearls as possible and see if it will be possible to differentiate between types just by photoluminiscence spectrum. One has to run a lot of pearls through before making any conclusions but I am inclined to the pearls in the necklace being akoyas.

Conny

 

[pattye]

Well, we do love seeing the scientific photos and appreciate your posting them with the explanations so very much. It's fascinating! And I do hope for some resolution about what kind of pearl these are. Do the drill holes seem large, such as 1mm?

I'd have cut the thread long ago and had a peep down the hole, lol.

 

[Conny Forsberg]

Pattye, the drill holes are pretty narrow but seems worn at the "mouth" of the hole. A bit funnel shaped. My guess is that the knots have been "eating" on the nacre during the years. That is a wild guess though...

Conny

 

[pattye]

It's somewhat surprising the thread doesn't appear more stretched for as dirty as the pearls are. The thread doesn't appear to have aged as silk does, and which would be gentle on the pearls. Perhaps the strand was restrung at some point on something other than silk. I hope we will see photos of all this and eventually the cleaned and restrung necklace.

Do the pearls see somewhat lightweight for their size? I know you said you don't deal with pearls much, but often keshi pearls are noticeably lighter compared to similar size cultured pearls.

 

[GemGeek]

I love this thread. Great advice from Pattye and Dave. He is right that their age would make them likely candidates for akoya pearls. I'm still hungering for a natural light photograph. If only I controlled the sun!