Orient color

[Caitlin]

I have been following this thread for a while- peoples' thoughts are quite interesting on the subject of orient-[FONT=&quot]iridescence - as is the science.

[/FONT]I had to comment though, when you have Paspaley claiming the territory as though his pearls weren't just mammoth pearl plated beads- which they are- I start getting a sour stomach. Even though SSP nacre can be thicker than akoya nacre- 1 or 2 millimeters can't possibly give you much depth. I think Tavernier is laughing while the cultured SS pearl producers try to jam Cinderella's slipper on their big feet and claim the prize of translucency!

I never did like the Paspaley Mystique (only real with a capital M). I saw several of their biggest and best necklaces at the Tucson AGTA Gem fair in 2005 or so. Stuller was celebrating their new partnership with Paspaley and had some giants on lend at the show- "The Athena", "the Diana" "The Texas", The Grandiose" and a couple of other such goddess names for pearls of such size as rarely seen before in cultured pearls and I dare say never seen before in the old natural pearls. In these pearls, roundness and size trump all other attributes.

None of the Paspaley giants had any orient I could see. I thought they were rather on the dull and flat side, bland even. Their main thing was the size- and that was beyond a human scale. The Stuller folks allowed me to try a smaller version of the [FONT=&quot]behemoths [/FONT]on- which I did. I held it and looked at it carefully from many angles and my final thought was, "so what"?

My daughter, who has an eye for seeing pearls --was not impressed by the Paspaley pearls - I think we saw a good range of samples in the display and none of them had anything like the iridescence in a freshadama strand (though we did not have that basis of comparison back then).

However, to read their website, you'd think they invented pearls and have the lock on what a pearl is. I beg to disagree. That final remark Steve quotes about perfect thickness and quality of nacre showing orient makes me want to gag. They have a huge stake in making their pearls appear the equal to, or superior of, old fashioned natural pearls- but they aren't- the SS cultured pearls Paspaley and others produce are just the best that can be done today, they are not the real thing, no matter what a court may have said.

As for that "only salt water pearls exhibit orient" remark- I think they should take that down. They are so very wrong and anyone who has seen a freshadama knows it.

Another thing, until this forum started making orient a criteria in 2006, it wasn't one for most people and Paspaley could use the term however he chose -much like the orient in the Emporer's new clothes, if you ask me!

 

[SteveM]

(i.e. enough translucency to see it as an independent phenomenon)

The point of view that I have attempted to 'champion' in this thread is that of natural pearlers I've been fortunate enough to meet, who use the term 'halo' (these folks never heard of 'water', by the way). Said 'halo' is assumed to come from either translucency (perfect platelet arrangement), or regular 'irregularities' (droplets) of nacre on the surface that bounce the light around a bit around the edges (diffusion?or whatever the correct scientific term for that may be). Given the natural iridescent properties of aragonite/nacre crystals and platelets, one must assume that iridescence is inevitably folded into the package as a secondary result. My introduction of the non-industry term '3-D' in this thread attempts to allow for both 'halo' phenomenae (rare to the point of extinction?along with naturals), and also to account for modern interpretations of orient such as iridescence that appears to float, or sink below the surface.

Paspaley: Posted simply to point out a concept of orient divorced from spectral considerations.

Steve
Seattle

 

[Valeria101]

... 'halo' is assumed to come from either translucency (perfect platelet arrangement), or regular 'irregularities' (droplets) of nacre on the surface that bounce the light around a bit around the edges ...

Would have loved to see such an example!

From the description, this sounds like a 'white' and more subtle version of the 'fish-eye' effect on black pearls. What do you think?

Something I have found on a couple of freshwater pearls too... but not yet on any white saltwater (most likely, lacking exposure).

Why am I asking: because the thin layer interference model suggests that such a 'halo' effect should be observed if the translucent layer is thick enough ... which would mean a nicer pearls (i.e. more translucent - whether that is called 'water' or 'eye' or 'halo' or by whatever name).

 

[KAC]

well I'm not getting involved with this oreint conversation, as i get a little tired of every conversation being steered back to the almighty freshwater pearl.

Maybe Jeremy or one of the other pearl vendors on this site will know more about that ( child labor issues). I think I read in a recent article from national geographic that the the legal age in China to hire someone at any type of job was 16.

As per this comment, I have been to Freshwater and Akoya operations in China and never have I seen a child working. I've seen young women possibly as young as mid teens but children never.

 

[Caitlin]

Sorry to offend you (again!) You must have noticed I have not touched this subject since February! That must be hundreds of posts!
But Paspaley claiming only salt water pearls have orient is just plain wrong and deserves a short turn on the podium.

Hi Steve
I think the term "water" has not been used in a hundred years, until someone introduced it here as criteria for a gem quality pearl. Then suddenly everyone was seeing "water" in their pearls........ I'd like to see some really old natural pearls with "water", then we would know what we are talking about. Otherwise, I am in favor of skipping that particular term for any and all cultured pearls.

Hi Ana
I can't find my copy of a book called the "Splendor of Iridescence" by Hilda Simon that goes into the subject of refraction, especially for feathers and suchlike, but my memory is that technically, iridescence may not be a synonym for orient in a pearl. Even so, it is still my preferred term. The use of "orient" and/or iridescence" may well be decided by popular use, no matter what the technicalities are.

In a similar example of popular use winning, Strack insists that pearls don't grow in oysters--- and technically they don't, but popularly, pearls are said to grow in "pearl oysters" and I doubt that Strack will win this one, in English at least.

 

[jshepherd]

Strack may pull that one off, actually. Although CIBJO uses the term "oyster", the GIA is now moving to mollusk. The next version of the pearls course only uses mollusk and mussel.

 

[Valeria101]

Hi Ana
I can't find my copy of a book called the "Splendor of Iridescence" by Hilda Simon that goes into the subject of refraction, especially for feathers and suchlike, but my memory is that technically, iridescence may not be a synonym for orient in a pearl.

Even so, it is still my preferred term. The use of "orient" and/or iridescence" may well be decided by popular use, no matter what the technicalities are.

Thanks for the reference, the title is new to me.

At this point, I am not so much interested in defining any popular term ('orient' or whatever) as to exploring the physics a bit. What could be a useful model of a pearl ?? What could be more exciting! (you get the picture).

well I'm not getting involved with this orient conversation, as i get a little tired of every conversation being steered back to the almighty freshwater pearl.

At least on my side, there is no intention to specify any type of pearl. Quite on the contrary. If it sounded that way, it is out of carelessness.

 

[Caitlin]

i get a little tired of every conversation being steered back to the almighty freshwater pearl.

Ana, I think he is referring to me saying freshadamas have better orient than SSP. Still, I think "every" is a little too strong a word........

 

[pernula]

Skimming thought the thread, there are a couple of places where translucency and iridescence (using this word for now, to keep away from 'orient') are implied to be disjoint: i.e. iridescence can happen w/o translucency, and the other way around. The 'other way around' seems straightforward - a sort of dull pearl.

But... if iridescence comes from interference, the nacre has to be translucent in order to let light get though some of the outer layers.

What gives? Is it a matter of degree you are talking about? (i.e. enough translucency to see it as an independent phenomenon)

And, what would be an example of pearl with strong iridescence and no translucency to talk about? My mind draws a blank on that one ...

(1) It only takes a very thin layer, on the order of the wavelength of light, to have interference and iridescence. For example, iridescent soap bubbles have very thin walls.

The visible spectrum is about 0.4 to 0.7 micron (one micron is one thousandth of 1mm, i.e., 0.001 mm). The aragonite platelets in the nacre of pearls are about 0.5 micron, so they are perfect for visible light interference. There is no way human eyes can see down to 0.5 micron. So you can see iridescence without necessarily having a visibly distinct translucent layer.

(2) Translucent materials allow light to pass through diffusely, producing a distorted image. If you put a light source behind something, especially if the light is bright enough, you can see the translucent property better. Apparently translucency is quite common. This http://www.neilblevins.com/cg_education/translucency/translucency.htm has nice pictures that show that leaves are translucent. I mentioned in my earlier post in this thread that the play of color of pearls seem to be three dimensional, like seeing through fog. It seems likely that the combination of thin film interference (described in part 1) together with absorption, reflectance, and diffusion of light in Fig 2 of the link creates the depth perspective.

(3) What is the minimum thickness of translucence for it to be visible to us? That depends on resolution of human eyes. Not an easy question to answer. Looking at a ruler, I think we can go down to 4 divisions (or more) of 1mm, i.e., about 0.25 mm. This http://www.clarkvision.com/imagedetail/eye-resolution.htmllink estimates the resolution to be 530 pixels per inch, or roughly equivalent to 0.05 mm dot. So I think generally we can see a distinct translucent layer if it is about 0.25 to 0.5 mm thick. Someone with very good eyesight may be able to differentiate down to 0.05 to 0.1 mm.

Translucency without iridescence, if the material is good color, is beautiful in its way. I am thinking of chrysoprase, jade, blue agate, etc.

Regards,
pernula

 

[Valeria101]

(1) It only takes a very thin layer, on the order of the wavelength of light, to have interference and iridescence. For example, iridescent soap bubbles have very thin walls.

Yeah! Thanks for the wake-up call from the garnet example and pearly dreams! I would hope that in the end the 'full package' of pearl quality characteristics I'm used to think of should actually make sense, objectively. But they may not... as the combination is a cultural thing, after all.

Pernula and all other members that participated in this thread:
Very interesting reading although it does not make it easier for the common consumer to get educated about such complex ...
For myself it does not matter what exactly it is, as long as the "rainbow shimmer" is there.

Well... yes... clear that.

Got to admit I like looking under the hood of things, so for me those obscure details are a core part of pearl appreciation (desperate case, I've been told before). And I am really thankful to have found a place where such musings are not emptying the room!

I am practically trying to poor my heart out rather than bore everyone to death or worse.

Even practically, yes, I do care where the iridescence comes from - someone's proprietary 'shoe polish' for (enhancing) pearls, or a little bivalve acting under duress or by it's own accord. LOL! Besides, the gritty 'interference' means the same for everybody, while the poetic 'orient', 'iridescence' and what not are forever disputed. In a sales environment, hearing those nice words brings in the image of a ... fisherman dangling his bait. Here, hearing them w/o the accompanying sound of pearls tossed in the hands of a jeweler is like reading though a dictionary with the right hand column missing ...

 

[pernula]

Very interesting reading although it does not make it easier for the common consumer to get educated about such complex sciencies.
For myself it does not matter what exactly it is, as long as the "rainbow shimmer" is there.

Sorry to take up bandwidth. Just fun to see the science being applied to something beautiful.

Here, hearing them w/o the accompanying sound of pearls tossed in the hands of a jeweler is like reading though a dictionary with the right hand column missing ...

I love the sound of strands of pearls too...

I think the merchants are having sales this weekend. Got to get out of the house.....

Regards,
pernula

 

[jshepherd]

Don't forget the feel of strands - large hanks that you can pull over your arm and examine in different light while walking around.

 

[Valeria101]

Don't forget the feel of strands - large hanks that you can pull over your arm and examine in different light while walking around.

Yeah! The very first time I have ever looked for pearls (and the only time in the south of Spain) sellers were rattling the pearls bunched in their cupped hands to demonstrate quality. The ocasional local customer around us looked and listened knowingly, but I had no clue what to make of it. And the situation has not changed What's up with that?

 

[Caitlin]

I think the pearlmonger rattle comes in klinks,klanks and klonks (though they may not be called that in Spain).

The ear can readily distinguish each sound. Trained ears can distinguish even more gradations. You would know they weren't fake or had glass beads inside by the sound. Faux pearls don't clink, clank, or clonk (I think the first spelling is Germanic, the second English)

Klinks are the sounds small pearls make when you rattle them. Clanks are the sounds of medium sized pearls rattling. and of course, klonks are the big pearls.

Then if you like the sound and take a strand in your hand, the weight should feel right. It does not take much pearl handling to realize glass beads are heavier than real ones, plastic ones are lighter.

Your ears and hands will tell you what the vender might want to conceal.

 

[Valeria101]

Hm... I see what you mean (I think), Caitlin, but the practice of 'rattling' them pearls was not about size, but quality.

Without this thread I wouldn?t have though of the matter in time. It so happens I am at a conference now in San Sebastian?(awesome place, btw ). I'll try to get some answer about this bit of local pearl 'folklore' from the source, although this doesn't look like much of a fine jewelry hub, at first glance.

 

[Caitlin]

HI Ana
Please do.

I think bead nuked pearls still rattle quite nicely, because the bead is not glass or plastic, but is very similar to a solid nacre sound. Majorica pearls or other faux pearls don't sound the same, so let us know why they think they are doing it.

BTW Amazon is selling the Splendor of Iridescence for $2.99 or so, so if postage isn't horrific, it might be fun to have. The author, Hilda Simon, also did the illustrations by hand instead of using photos. It is from 1971.

It is loaded with little illustrations of the cellular structure of iridescence in various bird feathers, butterfly wings, soap bubbles and other such pictures and how they defract light.

 

[Valeria101]

HI Ana
Please do.

I think bead nuked pearls still rattle quite nicely, because the bead is not glass or plastic, but is very similar to a solid nacre sound. Majorica pearls or other faux pearls don't sound the same, so let us know why they think they are doing it.

So I did... in three shops that came handy. Two sellers stared at me rather obliquely, the third was just starting to make a face when a much older colleague caught the talk from the back of the shop and came up with a story: his father used to do this! And this is coming from a guy in his 70's... Either the times are moving way faster in the North (the economy has, for sure) or I was really lucky the first time around to witness a dying habit. Anyway the explanation came that the gesture was meant to discern real pearls from fake (as you say, Caitlin) by mass, roundness (by the flow of the pearls) and nacre smoothness by specifically moving pearl on pearl slowly, with a bit of preassure. The last stage was meant - the fellow said - to guess whether the pearls may have been 'waxed' (probably he meant coated or such), whether they were polished or - lo and behold - summer or winter harvest Aparently, the noise made by the pearls is/was never meant to mean anything. He admited that he does not know to judge pearls that way - only heard the story. The first time I saw this done yars ago (and didn?t know to ask anything smart), the jeweler only mentioned the noise - 'listen to the pearls!' - which may well mean that he did?'t know as much or didn't think twice to waste one more word on me... or both.

Now, I must say that the walk through nicer jewelry shops here was a real treat, with some nice examples of cultured pearls on sight. Out of the blurr of mostly storm colored rounds: a rope of 10-15mm mixed color Tahitian semi-round and high buttons, 13mm lead-gray round in a choker, lots of black earrings, rings and what not. Very few whites looking out of context in slightly dated evening settings among the majority of trendy day and office wares... a few goldens in high esteem and a stupendous long rope of pinkish white to dark creme keshi - the largest as big as my thumb (was that a mix of frehwater and south sea? )... you get the picture. No other pearls that I could see. But again, this is one of those surreal places with no notion of luxury since most things in sight are just that anyway, by default.

That's the story I've got, at least.

 

[SteveM]

now in San Sebastian

Spend a lot of time in Spain as it's our primary source (wine) over the past 25 years. Recent business trips have added pearl gazing to the itinerary?

My wife and her mother arrive on a flight from Madrid this evening. My mother in law is a lifelong pearl lover who just celebrated 88 glorious years. I'll be asking her a few questions over the coming weeks (BTW she loves the strand of untreated freshwater baroques from Pearl Paradise she received for her B'day!).

Steve
Seattle