[Perle]

Hi Jeremy,

Thanks for the additional info, and Happy Father's Day! If you don't mind (!), I'd like to ask one or two more questions, but I'll take it offline – don't want to bog down the thread.

Because I'm sure we all want to know: what's this about exotics and untreated pearls?!!!

Perle

[pernula]

Thank you Inge and Perle for the warm welcome and kind comments. I learn a lot reading this forum.

I went to buy pearl necklaces from a jewelry store a couple years after I started working, armed with no knowledge. At the store, I was shown necklaces about 10X price differential. While I could see there was a difference in how shiny they were, I could not tell what else set them apart. The person at the jewelry store told me that it was very difficult to judge pearls, that in Asia they had to train girls at a very young age to sort pearls. Feeling intimidated and horrified at the prospect of child labor, I ended up buying opal jewelry instead. Looking back, the jewelry store owner/employee was actually really nice and patient, as most jewelry store folks would ask for a budget and then would be very reluctant to show things out of budget. But then she probably wasn't so knowledgeable either. Anyway, I just want to describe what I saw in pearls to find out whether I am seeing the right things....

[pernula]

Hi,

I forgot to put in the correct descriptive phrase in the last post. (I don't know how to edit a posted reply). What the jeweler told me was that they had to train very young girls with good eyes to sort pearls. After a certain age, you just can't learn the stuff. I was so intimidated! (I was only two years out of school then but I am someone who has to wear glasses.) I hope they don't use laborers under a certain age in pearl sorting.

Regards,
pernula

[Casey.R]

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.
When you get into the specifics of materials used in jewelry some do have some undesirable elements to them. I mean we all know about diamonds and I hear things aren't always peachy at some platinum mines either. I could go on.... but I won't.
I guess there are things you can do to be extra careful if your concerned.

[jshepherd]

Although the workers do look young, none of them are below the legal working age. I am not certain what it is, either 16 or 17, but I do know that the law is more strict than the US law which allows for younger part-timers.
I have seen girls that were too young to take a job at a farm learning nucleation techniques in a separate shed, but this was so they would be ready and able to work when old enough.

I am only speaking about the pearl farming industry, however. This is not likely indicative of all of China.

[jshepherd]

No, it is not a coating. Coatings are typically easy to spot. You should be able to stick a pin into a coated pearl and see the coating.

The luster treatment is in two stages. The first happens with maeshori. The pearls (in most common method) go from hot to cold, to hot to cold. This tightens the nacre, and is considered a "pre" treatment.

The second is after bleaching and is a chemical treatment, but heat (in the form of warm water) is also used.

[Gemsveritas]

Originally Posted by jshepherd

No, it is not a coating. Coatings are typically easy to spot. You should be able to stick a pin into a coated pearl and see the coating.

The luster treatment is in two stages. The first happens with maeshori. The pearls (in most common method) go from hot to cold, to hot to cold. This tightens the nacre, and is considered a "pre" treatment.

The second is after bleaching and is a chemical treatment, but heat (in the form of warm water) is also used.

Thank you Jeremy! Fascinating to learn so much that is not covered in my gemmology course. Pearls are more-or-less lumped in with the "organic gems" in my study guides. Maybe now that pearls are becoming more popular, gem(m)ology education will increase their coverage.
Regards

[smetzler]

Originally Posted by jshepherd

maeshori…from hot to cold, to hot to cold.

Yet another wrinkle… I refer to Caitlin's thread 'Long term pearl care' in which I rhetorically inquired whether pearls can go 'in and out of tune' (pardon the musical analogy) in terms of lustre. I've since paid for downloads from unintelligible scientific sites on the characteristics of nacre (vs. manmade ceramics) and can't help but continue to wonder if between aragonite and conchiolin there exist transitory properties subject to temperature/humidity. Maeshori seems to indicate that nacre is potentially subject to environmental articulation.

This would supposedly apply to anyone's definition of "orient".

Steve
Seattle

[CortezPearls]

This round pearl has a clearly seen overtone...

The baroque one -due to its shape- does not have this clear overtone...but it is iridescent thus having orient.

Mother-of-Pearl shell shows diffraction...which we could call orient because it is so similar.

Some pearls will have several intense overtones (fish eye or "ojo de pescado" as we call it in Mexican Pearls) forming an optical "bullseye" of rainbow colors, and some have intense orient...but I have seen few pearls having both intense orient and intense overtones.

[Casey.R]

Now thats what I would call orient too! I do love sea of cortez pearls....sigh.

[smetzler]

Originally Posted by CortezPearls

…it is iridescent thus having orient.

Coming full circle! The pearls and shell are more than beautiful—they're fantastic. Need to get some…

But for the purposes of clarification, am I to understand that the antique glass bottle in my post #19 has 'orient'?

Steve
Seattle

[Valeria101]

Originally Posted by smetzler

But for the purposes of clarification, am I to understand that the antique glass bottle in my post #19 has 'orient'?

I don't know that particular bottle, but couldn't find any better one-word description for iridescence occurring throughout the volume of some material (i.e. NOT a property of the surface layer only). Colorless roman glass comes to mind as a better example. Not that catching that effect in photography of ancient glass is that much easier! The exact image I have in mind (transparent, near colorless glass with iridescence showing with movement) didn't come out from Google Images, this one from the conservation centre in Liverpool comes close:





And these: LINK with physical explanation of the property included



But would rather reserve the term 'orient' for pearls, as it is done already.

There may be other gem materials prized for the spectacular effects of thin layer interference. I am not sure off hand if fire agate, opal, ammonites and feldspars owe their iridescent colors to the same effect. Besides, I expect consistency of the iridescent layers to be part of the 'look' called 'orient' - i.e. iridescence combined with translucency and depth, not a visible sheet as it opal, or from internal fractures in some stones (e.g. 'rainbow' quartz). So that one gets to see the progression from translucency to the iridescence at the right angle uninterrupted, as it happens for pearls and little else. Picky!... I know...



2c

[jshepherd]

What a scientific analysis there, Valeria! Thin layer interference is the best description that I know of, also referred to as thin film interference.

But what is important to point out is that not all pearls will exhibit this. Sure, the color expressed in the pearls above is referred to as orient. As are the colors that move around a Tahitian pearl. In the industry, we call it orient. But academically, it is not. Tahitian pearls canNOT have orient according to CIBJO and every gem lab in the world, but according to the industry they can. This is because visually you see the play of colors (the classic soap bubble or oil-slick look).

This could be a big debate that goes on endlessly with every producer emphatically claiming they are right. White South Sea producers claiming South Sea has the best orient, Tahitian producers scoffing at those claims and claiming Tahitians have the best orient, akoya producers claiming the same orient combined with luster, and freshwater producers... etc, etc, etc. I know there is a debate going on behind the scenes even now, with specific segments upset at me for describing the true academic meaning of orient.

Like I said before. Every pearl producing segment in the industry has their own definition of orient, and it best suits their own production. This should not be a big issue. It is the highest value factor in each segment.

May I also suggest just coming out on this thread and debating individual views? What could be better than competing producing segments having an open platform to tell the world why their orient is the right orient.

[smetzler]

Originally Posted by Valeria101

…would rather reserve the term 'orient' for pearls, as it is done already.

…'orient' - i.e. iridescence combined with translucency and depth…

Superb post! This thread should be a lesson to all forum members not to be afraid to ask dumb questions—with results like that.

I am completely comfortable with the two summary points above by Valeria as a satisfactory use and understanding of the phenomenon.

Steve
Seattle

[Casey.R]

I'm editing this too.