What, exactly, is bad about difussion?

[beginswithT]

These are the things I know about diffusion sapphires--
1. color is added to the top layers of the stone
2. it''s considered a bit a of a no-no around here
3. it can''t be re-cut ever
4. it''s cheap
5. it should always be disclosed to the buyer

Here are my questions--
1. Does the color ever fade with normal wear and tear?
2. Why is it considered such a no-no?
3. Can an average person tell the difference?
4. Does it look nice to the naked eye?
5. If it''s disclosed, and a reasonable price, why not?

 

[valeria101]

Those stones look dazzling - there is barely anything in nature as hot. Now, "cheap" depends on how you define it. How about this one... proper disclosure included:

Obviously 1k/carat for a 7 carat ruby or 0.6k/carat for a 7 carat hot orange sapphire are tremendous bargains, but then... doesn't Ramaura look at least as well ?

Nothing inherently "bad" about color enhanced sapphire comes to mind. The stuff looks spectacular. To me, this is just one clever method to produce high-end synthetics. Admittedly, the line between lab-made and not is more blurred here than usual, hence a premium over colored crystals made of raw material that doesn't look remotely like the finished piece. After all, it was sapphire that went into the oven this time, not only some obscure chemical concoction. If this makes sense to you, than why not go for one.

Not my personal feelings necessarily, just one way to look at this. I have not followed the story aside the disclosure scare seriously enough to see who uses larger color enhanced sapphire and for what ends. If I were under pressure to buy a seven carat ruby for dinner, perhaps I'd have some reason to think harder. As is, these guys just look intriguing.

 

[strmrdr]

Its close enough to synthetic that id rather just get synthetic and save some more money.

But the bootom line with me and gemstones is buy the stone not the paper.
The paper just determins the cost of entry.
So I could see myself buying one.

 

[Sasori]

I would rather get a synthetic stone than a diffusion.
Why get a "wolf in sheep clothings" when you can get a "cloned Dolly"?

So BeginswithT, have you found your round stone yet?

 

[Colored Gemstone Nut]

Here are my questions--
1. Does the color ever fade with normal wear and tear?
2. Why is it considered such a no-no?
3. Can an average person tell the difference?
4. Does it look nice to the naked eye?
5. If it's disclosed, and a reasonable price, why not?

Diffusion is the process of surface coating the gem with cobalt baked onto and partially into the sapphire. Diffusion bakes the color into the surface of the stone with minimal depth.

To answer your first question this type of diffusion is not permanent. The true color of the original stone will begin to show through with wear and scratches. Diffusion treated sapphire is cheap, but the trade off can be temorary if your hard on your stones.

A tell tale sign is when a gemologist test the stone for refractive index. The reading will show faint or weak.

Your 3rd question: Can an average person tell the difference? In most likely all circumstances no..Diffusion treated sapphires share all the same characteristics as you would normally see in a heated gem such as normal inclusions from the result of the gem being heated. A halo affect is also seen around the inclusions where some of the crystal started to melt which is also a normal indication of heating.When turning the stone under close inspection you will spot an abnormally dark concentration of blue in certain areas of the stone. This concentration will appear on the top of the gem rather in the color zone normally present which is viewed inside the gem.

The true confirmation of this diffusion is done by the professional using a spectroscope and chelsea filter.Chelsea filter works by allowing only certain wavelengths of yellow-green and red colors to be transmitted through the filter.Using this filter the color of the true gem is more apparent and you can reaadily view the surface layer used. A diffision treated sapphire has a particular signature while using the spectroscope. There are 3 absorption lines which are viewed using this instrument for cobalt which differ from the normal iron absorption line which is also viewed simultaneously in the same gem.

Questions 4 and 5 are all personal preference. If it’s cheap and disclosed properly and pleasing to your eye, Why not if your satisfied. Be aware that the treatment over time might not be permanent though. Color is king in the world of gems and personally I would want something more permanent..

Hope this helps..

 

[rubydick]

Allow me to answer your questions in order:

These are the things I know about diffusion sapphires--
1. color is added to the top layers of the stone

While true with diffusion of heavy elements (Ti, Cr), this is not true with the modern diffusion of light elements (Be). These may penetrate deep into the stone, or completely through it.

2. it's considered a bit a of a no-no around here

Mainly because Be diffusion was first introduced into the market with a series of statements which were, in the opinion of many, misleading. Thus the reputation was set.

3. it can't be re-cut ever

Recutting those stones with shallow penetration may result in loss of color; those with deep penetration (mainly yellows) may be safely recut.

4. it's cheap

This is because the starting material is cheap. Bulk diffusion is essentially the same as dying a stone. Within certain limitations, production can be expanded as the demand increases. Thus it is cheap.

5. it should always be disclosed to the buyer

Amen.

Here are my questions--
1. Does the color ever fade with normal wear and tear?

Generally no.

2. Why is it considered such a no-no?

For a couple reasons. First, there has been a fair amount of fraud, via non-disclosure. And second, because certain parties manufacturing and selling these goods often have a nasty little habit of partial disclosure. They have poisoned their own well, so to speak.

3. Can an average person tell the difference?

This is immaterial. The average person can't tell if something is glass or diamond. As Thomas Pynchon wrote in Gravity's Rainbow, "if they can get you asking the wrong question, the answers don't matter."

4. Does it look nice to the naked eye?

See No. 3 above.

5. If it's disclosed, and a reasonable price, why not?

Absolutely. If it's properly disclosed, let the buyer decide. I've got no problem with that. Nor does anyone else that I know.

For more on this topic, see:

The Skin Game

Questions about Treated Sapphires from Thailand

Understanding the New Treated Pink-Orange Sapphires

 

[Colored Gemstone Nut]

Richard: In response to this statement...
4. it''s cheap
This is because the starting material is cheap. Bulk diffusion is essentially the same as dying a stone. Within certain limitations, production can be expanded as the demand increases. Thus it is cheap.

I have read articles by AGTA regarding bulk diffusion and does this not differ from cobalt diffusion. Using berylium to treat this sapphire rather than cobalt? Is bulk diffusion used more in the treatment of padparadascha sapphires

In using cobalt they coat sapphires before heating rather than putting beryilium into the kiln and heating with the batch?

 

[rubydick]

Josh,

Good question. What is the difference between "diffusion" and "bulk diffusion" and "surface diffusion" etc.

I'm not an expert, I just have smart friends. And they have enlightened me on the difference between these terms. Here's my admittedly mangled understanding of what they've taught me:

When any material comes in contact with another, there may be an exchange of atoms. That exchange is known as "diffusion." In some cases, the exchange is mainly outside-in, in other cases, it is mainly inside-out. But the exchange always takes place and always in both directions. It is simply a movement of atoms.

When the diffusion is mainly outside-in, it is referred to by serious scientists and others with seriously thick glasses and pocket protectors as "bulk" or "mass" diffusion. In other words, lots of outside atoms penetrate the bulk or mass of the other material.

When the diffusion is confined primarily at or parallel to the surface layers, it is referred to as surface diffusion.

In the past, gemologists used the term "surface diffusion" to refer to a process that real scientists termed "mass" or "bulk" diffusion.

Today, gemological labs such as the AGTA, GIA, SSEF and Gubelin have agreed to correct their nomenclature, to bring it in line with general science. Thus today, they refer to such stones as "bulk" diffusion.

So to answer your question about cobalt, let me generalize. It doesn't matter what the element is. If you create conditions that allow substantial outside-in penetration of a foreign element into a gem, you are engaging in a treatment process of "bulk" diffusion.

Now keep in mind that all heat treatment involves diffusion. Here I quote from an article I wrote a few years back:

"It has been suggested that, since “traditional” corundum heat treatment involves diffusion, that these [Be-treated] stones should be considered the same. Is this true?

"Again, in our opinion, no. “Traditional” in terms of corundum heat treatment was previously defined and agreed to by the world's gemological labs and trade associations as “heat only.” These agreements included Thai gem trade associations and labs. Scientifically speaking, such “heat only” actually involved diffusion of hydrogen. This is not a new discovery, and has been understood for well over a decade. But when these stones first entered the market in the late-1970’s, this was not understood, and so dealers were sold these goods unknowingly. Thus a special exemption was made for them.

"Certain parties in Thailand now ask that a special exemption also be made for their beryllium-diffused goods. But if special nomenclature exemptions are possible every time a new treatment appears, the current system, which has taken years of tedious meetings to put together, will quickly become a useless swamp of special interests. The world gem trade/gemological community has been hostile to the idea of a beryllium exemption, in large part because the warnings went out so quickly that most dealers abroad did not get stuck with the goods. Thus they were free to make an unbiased judgment because they did not have a stake in the outcome. In other words, they were free to choose between doing the right thing and the selfish thing.

"After January 2001, beryllium diffused goods have mostly been “buyer beware,” an idea that is well understood in Thailand. The fact that some dealers in Thailand have continued to trade these goods, knowing the potential risks, is their business. But ignorance is no longer a valid defense."

Hope that is of some help.

 

[Colored Gemstone Nut]

So to answer your question about cobalt, let me generalize. It doesn''t matter what the element is. If you create conditions that allow substantial outside-in penetration of a foreign element into a gem, you are engaging in a treatment process of "bulk" diffusion.

Thank you Richard..

P.S.-Sure you don''t have thick glasses and one of those pocket protectors or do you stroll through Burma with your Oakley''s on...

Thanks Again..-Josh