overtone versus orient

[Zeide Erskine]

Hi Cam,

That can be done, yes. It helps to keep a written record of which is which. Chances are, that showing one of those strands to customers might harm your South Sea and akoya sales, though.

Zeide

 

[Zeide Erskine]

Hi Richard,

Please do forward them to Fred for a photo-op. You may also recruit your wife as a model for distance tests, i.e. let her wear them and observe them at a distance. There is probably little use to compare the teaching strand to how other strands look at a distance because of the size issue. However, if you have comparison strands in similar size, that would be a good idea.

Zeide

 

[Richard W. Wise]

Hi all,
Well Fred Ward may not join us but he is willing to take a shot at photographing orient. With Zeide's permission I will send the teaching strand along to him.

By the way you may be interested in my new blog post: Burma Journal; The Road To Mandalay. Just the thing for armchair traveling.

 

[Richard W. Wise]

Ziede,
More on this conchilin thing. The bleaching eats the conchilon? My understanding is that conchilin is a glue like protein binder although some call it calcium carbonate, that is between the aragonite layers. Sort of thought of it as a lasagna, aragonite, conchilin, aragonite but sounds like the binder is everywhere between the crystals.

Why does the lack of it result in "murk"?

Have seen overbleached or Japanese process pearls that appeared to peal.

 

[Zeide Erskine]

Hi Richard,

All pearls have conchiolin spread throughout and most also have the lasanga layering in addition. When the bleach destroys the conchiolin it destroys the translucent conncetion between the crystals. The murk factor results because the leftover aragonite crystal platelets stick together like salt crystals in a shaker that have become wet and clumped together. If the conchiolin is still present in the original form the aragonite crystals grew on, the crystals touch and light flows through them with less scattering than it would with these conchiolin bridges missing. When the conchiolin accumulates in higher concentration it serves like a mirror backing and when such thicker conchiolin layers are bleached, the resulting short protein fragments are a light mint green and opaque but not reflective. Overall, bleaching always requires additional treatments to remedy its negative side effects.

Zeide

 

[Richard W. Wise]

Ziede, et al,

Ok, the teaching strand together with two pair of pearls arrived. What I see is the effect that I describe in my book as 'rainbow irridescence' which I distinguish from "true orient" that I then confuse with overtone. Opps, will have to revise that one. Yes it is the same phenomenon as I have observed in baroque Chinese pearls some of which I have on hand.


Examined the pearls under magnification. They have an appearance that differs from the freshadama strands, they have no central shadow and they dont appear pink in transmitted light. If anything the pick up a bit of veining like the green veining in our skin. However, the round ones do have a central shadow and also turn somewhat pinkish so this may be a function of the shape.

From what Ziede is saying, chemical bleaching is responsible for destroying the orient. Great explanation by the way, seems like the source of orient is similar to the source of play of color in opal. Question now is, how do we get to the freshadamas before that happens.

I have to say thanks to Ziede for sending me the pearls. I am not sure that anyone can truly capture this affect on film but we shall try.

Richard

 

[National Pearl]

Orient within Akoya

Orient within Akoya

Ziede,

Concerning orient within Akoya pearls. I understand that it is very rare for Akoya pearls to exhibit true orient. In your experience, have you seen many Akoya that truly exhibit orient? As was stated earlier, it is not too uncommon for chinese freshwater to exhibit this quality, but I have yet to find Chinese Akoya that exhibit true orient, in my opinion.

 

[Zeide Erskine]

Dear Andrew,

In order for a pearl plated bead to have orient, it needs to have 30% minimum grown on nacre coating of total mass for a total diameter of around 8mm. Proportionately more for smaller pearl plated beads and somewhat less for bigger ones. That is, of course, the bare minimum to show any orient at all, distinct or strong orient would require more and any orient requires that the pearl plated bead has not been bleached. However, that means that akoya-type pearl plated beads can show orient and I have some both in the bead nucleated variety and the solid-nacre variety. The solid nacre kind is from the fin de siecl? (turn of the 19th to the 20th century) and the bead nucleated kind is from a Korean university research installation using pinctada shimitsuensis.

Zeide

 

[perlas]

In order for a pearl plated bead to have orient, it needs to have 30% minimum grown on nacre coating of total mass for a total diameter of around 8mm. Proportionately more for smaller pearl plated beads and somewhat less for bigger ones. That is, of course, the bare minimum to show any orient at all, distinct or strong orient would require more and any orient requires that the pearl plated bead has not been bleached.

Zeide,

In this case, do the akoya pearls maintain the metallic luster and at the same time possess orient or do they start to hold more "water"?

I have seen some loose akoyas with orient and they still appear to be metallic compared to freshwater pearls. But aren't akoyas usually bleached and treated? The akoyas I saw are the half drilled ones intended for earrings. I remember having a hard time matching a 7mm akoya because no other pearl can match the play of colors.

Since the pearl I saw was drilled and had it's bottom cut a bit (enough to expose the bead), I was able to see that the nacre is thick.

 

[National Pearl]

Thank you Ziede,

I did not know before this thread that bleaching affected the presense of Orient. You are a true pearl wizard!

 

[Zeide Erskine]

Hi Sam,

Akoyas are near universally treated except for the fancy natural colors and some Korean ones (that come from the closely related pinctada shimitzuensis) that occur in albino rosé. Some of these Korean farms are experimenting with extra long cultivation times and the quality (and price) reflects this. Orient will be destroyed by bleach but polishing does not affect it very much. Oiling seems to diminish orient a little bit and vapor deposition seems to have no effect.

Zeide

 

[CortezPearls]

Photos are useful

Photos are useful

This is a very interesting subject, but photos of pearls may lend some help. For instance, you can fully appreciate the Overtone on the pearls in the following photo.
Notice the "halo" effect...it cannot be fully appreciated on this small low-quality photo. Pearls that display at least 3 distinctive (sharp) "rings" or "haloes" are know to have the "Ojo de Pescado" or "Fish's Eye" effect, which made the Sea of Cortez a Legendary Pearl.

Douglas McLaurin
Perlas del Mar de Cortez

 

[CortezPearls]

Then...we also have ORIENT which is also very hard to capture on a photo since it is a dynamic visual effect that is best seen as you gently move the pearl. In this case, a photograph is a "static" representation that will never be able to give you the full effect.
Nevertheless, some pearls are so full with Orient that some of this incredible beauty -just a mere fraction- will be seen on the photo.

These baroque pearls are over 10mm in diameter and display good orient and overtones. It is easier to "catch" Orient on baroque pearls...their uneven surface allowing for a better play of colors.

Douglas McLaurin
Perlas del Mar de Cortez

 

[Slraep]

I was under the impression that orient is the result of reflected light and that body overtone is the result of absorbed light.

Slraep

 

[Zeide Erskine]

Hi Slraep,

Overtone is the result of absorbed light, mirror is the result of reflected light, and orient is the result of refracted light. In your standard cultured pearls, you typically have only one or at best two of these properties but orient is hardly ever one of them. I am glad you appreciate your object lesson in water, mirror, and orient. You really must have seen pearls that are absolutely untreated while simultaneously being of high quality to fully appreciate what the old masters were so keen about. My standard for pearl earrings is that if Vermeer saw them he would have wanted to paint them.

Zeide

 

[Cam Hatch]

Hi Richard & Zeide

Any luck with the photography of the strand??

 

[Slraep]

Overtone is the result of absorbed light, mirror is the result of reflected light, and orient is the result of refracted light.

So, the quality of mirror would consist of uniquely reflected light. The orient, on the other hand, would be due to light comming into the pearl, getting distorted by the floating layers/sheets of aragonite crystals and comming out refracted as if through a prism(thus the rainbow effect). The thinner the sheets of suspended aragonite crystals, the better the orient. The more of these thin suspended aragonite sheets, the better the orient.

Sometimes one can see the multiple thin concentric sheets of aragonite very easily. Between these aragonite sheets there is another colourless, translucent sheet of various thickness. What is this translucent sheet? Is it conchiolin? Or is it just a trick of light? There should be very little conchiolin compared to aragonite.

Slraep

 

[Zeide Erskine]

Hi Danuta,

The layers inbetween or what looks like layers inbetween are more aragonite layers where the individual aragonite crystals are facing in another direction. Hence the refraction. It makes me happy when other people finally understand why I want my pearls unprocessed.

Zeide

 

[Slraep]

Ziede,
More on this conchilin thing. The bleaching eats the conchilon? My understanding is that conchilin is a glue like protein binder although some call it calcium carbonate, that is between the aragonite layers.

Hi Richard,

Conchiolin is an organic protein. It is not a mineral, and so it cannot be any kind of calcium carbonate, even if some call it that. It is the aragonite crystals that are a type of calcium carbonate, in orthorhombic(twinned) crystal form.

Slraep

 

[Slraep]

Hi Slraep,

The layers inbetween or what looks like layers inbetween are more aragonite layers where the individual aragonite crystals are facing in another direction. Hence the refraction. It makes me happy when other people finally understand why I want my pearls unprocessed.

Zeide

Okay now, the transparent layers have been demystified! It couldn't be conchiolin because the percentage of it in a fine pearl compared to aragonite is just too small.

Slraep