Can someone fill me in on heat treatment?

[northstar_78]

I''m looking for an emerald cut or rectangular cushion or pear stone for a right hand ring. Being me, and based on my budget, I went to ebay.com. There are a lot of nice stones out there...pretty open color wise. I do love greens though but I keep hearing that emeralds are "soft" and for me that wouldn''t work as I would like to wear the ring every day.

Most of the stones that I liked were heated. How is this done? Is this done only on the commercial level or are there individuals out there who do it? The one stone I did like had a lovely color, shape and good size for my small fingers but it dd have some clarity problems. They appeared to be feathers, and clouds. I emailed the seller to see if that''s all.

Could heating it remove those flaws? Where could an individual consumer go to have this done?

On another note; help me find a lovely green stone harder than emeralds!

 

[Michael_E]

northstar_78,
Heat treating is usually done as close to the source of the gems as is practical. It is done to increase clarity and improve color. Even with the new found desire to have an "unheated" stone, most gems are heated because it makes the stone much more valuable, (since the stones that are heated are generally not very good looking straight out of the ground. Since the increase in value is so large the heat treating is often donevery close to where the stones are mined since the miners or those buying from them want to get the most money that they can for their stones. It would be a very rare stone that would make it to us that hadn''t already been treated, if that treatment would have improved it''s appearance. Heat treatment will not fix cracks, feathers, clouds or any other problem of that sort and would most likely make them worse.
Emeralds are not really all that "soft". They just tend to have inclusions that weaken them and can make them less durable than you might need them to be. Other green stones that can look similarly and are more durable are: Chrome tourmaline and tsavorite garnet. I have seen a couple of sapphires that have an attractive green color, but never that intense pure green of these other gems. Usually the sapphires are either yellowish or bluish and the greens are more a forest green.

 

[lonewoodminer]

Hi all
I agree with michael - a couple of points from our experience.
As a general statement there is nothing wrong with basic heat treatment. I still have problems with the use of irradiation and the adding of other chemical substances to significantly change a gem (enhancement). But in most cases (eg sapphire) basic heat treatment just evens out the colour of the natural gem by finishing the process started by nature.
Heating and enhancing a stone are two different things, but are almost always done just prior to cutting (not at the mining stage in the case of sapphires in Australia).
The other fact that is often overlooked is that heating a product like sapphire helps the seller by making the stone more even throughout a parcel. In large quantities the time involved in grading needs to be considered. Some of the stone heated as a matter of course would be fine natural but often in the large cutting factories to create a new category for a small amount of stone would cause more trouble than gain.

Cheers Andrew Lane
www.aussiesapphire.com.au

 

[mogok]

Hello northstar_78,
Heat treatment is performed on ruby and sapphire in order to improve the gemstone clarity, color or both. I is a very traditional practice that was performed for centuries in order to improve the aspect of such gems, but recently the technology had some serious evolutions. Now heat treatment performed on many rubies and sapphire has few things to do with the treatment practiced only 30 to 40 years ago. Currently modern gas and electric furnaces are used and additives such as fluxes are common.
Richard Hugues has written a very good article about this last aspect of ruby treatment that I invite you to read if you really want to get more information on the subject: you can find it on the following link:
fluxed up
Using heat treatment several inclusions present inside a gemstone can be fixed. It is the case for exemple for rutile silk clouds. Heating rubies is a way to improve then the transparency of stones which are too silky as with the heat the solubility of titanium in corundum will improve. Now regarding to fissures and other cracks heat treatment using fluxes will close the fissures and in some case the fissure will completely disepear. Most of the time a "fingerprint" will remain that will present typically this aspect:

As you can see, it is a typical "worms and droplet" design.
Now some some host cracks or fissures that have already undergone a natural healing process. These inclusions named fingerprint can looks for a non gemologist as the "worm and droplet" inclusions of gems heated with additives but most of the time their design is much more angular and complex as the cooling and healing process was very slow in the nature.

Now some inclusions can get much worse after heat treament. Crystals can melt and explose creating discoids, or some color patch can also happen.
In fact to know if a gem could benefit from heat treatment is a not an easy job an even skilled professional sometimes can do very costly mistakes. But if you want to take the chance you can come in Bangkok or Chanthabury in Thailand to heat your gem. Other place offer such services but their techniques are much more primitive and the result are not that good compared to the Thai burners.

If you want to learn more about how relatively traditional heat treatment is performed, you can see the photogallery I did on the following link after several trips and heat treatment runs in Pailin, Cambodia:
Sapphire heat treatment in Pailin
If you want to see the result of these heat treatment performed wothout flux like additive you can also study the following inclusion photgraph gallery:
Pailin sapphire inclusions before and after heat treatment

In the next few weeks and days I will put on line some other photo galleries about heat treatment in Thailand and Vietnam that you might be interested to see...

Anyway I hope that these explanations will be useful to you,

All the best,

 

[MINE!!]

Greens.. Try Tzavorite and Tourmaline.. both are beautiful!

 

[mogok]

Oups...
You were speaking about green stones? And I answered to you about reds and blue... I ''ve read too fast!
On green stones you can try garnets: Demantoids or Tsavorite, Tourmalines can also give some very attractive gems, other gemstones can also form time to time give interesting green but emeralds to what I have seen remain the best green I ever see if I except Jadeite.

Demantoids and Tourmalines are sometimes heated, Tsavorite not to my knowledge, Emeralds are not as it cannot survive to temperatures over 700 or 800 degres... Jadeite not to my knowledge also...
On these 2 last green stones the concern is so more about filling with resins, oils or other polymers. It hides the fissures but does not heal them really as flux in ruby heat treatment does. So the fissure even if it is not visible is still a hidden thread to the stone durability.

All the best,