Emeralds - Can they be coated?

[serenitydiamonds]

Date: 12/14/2009 2:38:31 AM
Author: Nacre

Date: 12/11/2009 11:00:10 AM

Author: serenitydiamonds

Date: 12/11/2009 9:55:12 AM


Author: Kismet

Date: 12/11/2009 7:33:56 AM



Author: serenitydiamonds

Date: 12/10/2009 10:13:29 PM




Author: Nacre




Tanzanites are not heat treated...






Green/brown Zoisite is heat treated to produce the blue colour called Tanzanite.

That is the definition of heat treatment. It is normal, and accepted among Tanzanite, but 99% is typically heated.





--Joshua

I think Nacre is just being overly literal. He's saying that the green/brown Zoisite is heated to BECOME Tanzanite and therefore the Tanzanite requires no (further) heating. If he's selling his Tanzanite as all unheated I suppose it would be true in a sense but I would certainly classify it as deceptive advertising.

Yes, I understand that, and yes that is still heat treatment.



--Joshu

It is very important to be specific when it comes to treatments. The treatment of Zoisite is acceptable as it is permanent and it mimics nature.


You cannot say, therefor, that Tanzanite is heat treated to become blue. That is misleading and incorrect.


Most Tanzanite on the market has been heat treated. I have seen natural Tanzanite. Often they cut these stones to leave in the green Zoisite as well for rarity value.


And one more thing - I am a Gemmologist. I do not appreciate comments like this. 'If he's selling his Tanzanite as all unheated I suppose it would be true in a sense but I would certainly classify it as deceptive advertising.'


Where is my advertising? Where am I selling Tanzanites again? I choose to remain avatar free and anonymous as I come to these forums to learn. If I have corrected you, build a bridge. This is a science and clients need to know facts about enhancements of gemstones.

There exists, in very small quantities, very small amounts of blue Zoisite, also known as Tanzanite, which has not been heated. Not matter what you heat, whether it be Beryl, Corundum, or Zoisite, heating is a treatment to the raw material. Yes, it is permanent, however, yes it is a treatment. An untreated material is defined as no processing other then faceting after mining. Every stone has it's range of acceptable treatments depending on tradition, marketability, and permanence. It is misleading to label something that is heated anytime during the manufacturing process, no matter the motivation, as untreated. I don't sell Tanzanite either, my only motivation is complete and clear communication of the treatments available in gemstones.

--Joshua

 

[Liane]

Date: 12/11/2009 4:59:00 PM
Author: anne_h

PS - Since you seem to know a lot about emeralds, if/when I ever want to find a high-quality stone, who are some vendors you might recommend? I''ve seen Embassy Emeralds online...

I''ve had good experiences dealing with Embassy Emeralds. Garrett (the guy who runs it) is nice, honest about disclosing treatments and flaws in his stones (a couple of the ones I was interested in had small windows that weren''t immediately apparent from the photos, but he was candid about admitting that), and prompt in responding to emails.

The stone I bought from Embassy Emeralds was accurately represented in its photos and is very pretty in person. I took it to a gemologist and it checked out fine (light colorless oil treatment, which is what it was supposed to be). Pricing is reasonable and in line with the quality of the stones; he has a variety of emeralds at different price points on his site and more that aren''t online.

I''m also working with the esteemed Mr. Griswold from this thread on a different project, but won''t have a report on that until sometime early next year.

 

[Nacre]

Date: 12/11/2009 11:51:39 AM
Author: LovingDiamonds

Date: 12/10/2009 10:13:29 PM

Author: Nacre

Tanzanites are not heat treated...


Green/brown Zoisite is heat treated to produce the blue colour called Tanzanite. Tanzanites are also showing on the market which have been coated (with I am assuming Be) but I am not certain on the coating material.



Emeralds can be Flux grown and Hydrothermally grown.


Both will show inclusions which can be mistaken for natural inclusions, seed plates and flux veils etc.


The most recognised natural inclusion in natural Emerald are the jagged three phase inclusions seen mostly in Columbian material. Synthetic Emeralds, to my knowledge, do not show these three phase inclusions, but they get better everyday with synthesis, so I could be wrong there!


Synthetic Emeralds as a rule show a lower RI, a lower SG and usually Flouresce strong red under LW and SW. Natural Emeralds are usually inert, or very weak under LW and SW.


If appraisal means certed, then you should know very soon anne_h!


I really hope things turn out okay for your stone. It''s always good to have a professional appraisal to keep your peace of mind though.

The coating is a cobalt coating and not BE diffusion that would permeate through the stone. The coating on Tanzanites is literally only on the surface and, thankfully, is not all that common.


You may find these interesting:


http://www.diamonds.net/news/NewsItem.aspx?ArticleID=23770

http://www.mayerandwatt.com/page/19

Hi LovingDiamonds,

Thanks for those Articles! I did go to Shane McClure''s lecture on coated Tanzanite, but I just couldn''t remember what the coating was. The coating contains Cobalt for the blue colour, but I wonder what it is? I guess they still don''t know.

I''m going to go and have a look at some this week to get my eye in again with them..

 

[Nacre]

I''m glad we both stand for disclosure of treatments, Joshua.