Cobalt-Colored Composite Sapphire

[Christopher P. Smith]

Hello everyone,

Today we sent out a release regarding these stones. They have started entering the market and so I am including our release here for anyone who is interested.

As with Composite Rubies, these stones should not represent a challenge for Gem-A students, graduates or knowledgeable appraisers who may come across them.

Best regards to all,
Christopher P. Smith

http://aglgemlab.com/news/2013/1/28/cob ... the-market

Just copy and paste in your browser's address bar.

[Egor Gavrilenko]

Thanks for detailed report, but isn't it the same treatment as so-called "Super Diffusion Tanusorn" known since 2007?

[Christopher P. Smith]

Hello Egor,

I am not always aware of all the names they give the various treatments however this may indeed be the newer generation of that particular treatment. At the end of our release, I compare this latest generation of treatment to the previous generation from 2007. The treatment has improved significantly from the previous generation and so I would not be surprised if more started to be encountered in the market, so I thought it a good idea to provide the essential information of how to recognize them.

Also, regarding the "name" of the treatment you refer to, if these are one and the same it is important to note that there is no true "lattice or bulk diffusion" taking place with this material. Cobalt has been added to the chemistry of the lead-glass portion of this composite material. No diffusion into the lattice of the host corundum is taking place.

Best regards,
Christopher P. Smith

[Egor Gavrilenko]

I can't see any substantial difference of the process, compared to that described in 2007: http://www.gaaj-zenhokyo.easystockhosti ... lead-glass

Were they ALL so opaque in 2007 as that one in your photo? GAAJ report already talks about "transparent to translucent material". The result of such treatment will directly depend on properites of the material to treat and can vary from one lot to another.

If there is no clear difference in the process applied, we can't talk about "new type of treated sapphire", IMHO.

[Bill Hanneman]

A sapphire (or ruby) has a hardness of 9 in the Mohs scale.
These items, do not have the hardness of 9.
All these items can be easily differentiated by simply testing with a hardness point if topaz (8). This is not a destructive test for corundum. Still, one might ask if the seller objects to your testing it in order to prove it is indeed corundum.

If the stone fails this test, The simple answer is, " It is not corundom." End of dicussion!