Heated Madagascar Sapphire
Madagascar sapphire has become one of the world’s top sources of fine blue sapphire. In addition to beautiful untreated material, treated stones have also appeared in the market.

To help separate unheated and heated Madagascar sapphire, Lotus Gemology has performed heating experiments to document the changes in these stones, even when treated at low temperature.

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https://www.lotusgemology.com/index.php ... tkvpaatnf4

12 Madagascar sapphires heated to 6 temperatures

Upon superficial examination of the article, it would seem as though heating the majority of sapphire from Madagascar results in both an aesthetic and monetary loss.

Heated sapphires command less money per carat and the before and after pics illustrated do not show much if any improvements.
Thoughts?

I think that whether you add vaalue by heating is related to how much visual improvement was made. In over dark stones, with too much grey/green component, and too sleepy from silk you can get a better, brighter, color and higher brilliance from increased transparency with melting the silk.

An attractive heated stone will probably sell faster and for more than an unattractive unheated stone. Anything border line should of course be left unheated. The changes in low temperature heating is not well understood in many labs, and they can pass for unheated many times.

The thing that is most interesting to me are the high iron content stones that are more typical in Basaltic Sapphire than metamorphic stones. The lightening of these with low temperature heating in an oxidizing environment has potential to add meaningful value.

Am I understanding the article correctly in the heating procedure? Each stone was heated to the set temperature then reheated to the next with a study done at each interval.

Yes

In the case illustrated above, Steve, do you see enough of an improvement to warrant the sting of added treatment?

Not to mention that if one ever wanted to date the sapphires based on included zircon xls, the heating would compromise results.

Yes, heating has and will continue to be a profitable thing to do with Sapphire. There is the opportunity to lighten over dark, reduce the green in strongly dichroic stones, and to darken light and colorless stones as long as there is enough Rutile in the stone to be absorbed and contribute to color. Melting of the rutile also enhances clarity and brilliance. There is also the ability to heal fractures with flux (different than glass filing). Repeated cycles of treatment are common place these days. You stop when you are satisfied with the results.

The fact that this can now be done in off the shelf ovens at $2,000 makes it a very valuable process to learn.

I hate to say it, but the changes in stones that have only been subjected to low temperature heat treatment are very subtle and are often missed in reports. The other side of that is that when the labs conduct experiments like this, publish the protocols and the results, it makes how to treat less a dark secret. More stone will get treated better because of articles such as this one.

I have about 1/2 a kilo of beautiful colored blue Sapphire that is over dark in tone. I will try some of the techniques shown here to lighten a few shades.

If your look at the pictures there are only two stones where somewhere in the cycle the stone is not a improved to some extent. Either by adjustment in tone, hue, or evenness of color. The key is knowing when to stop.

The article is excellent.

For burners the instructions are very valuable.

For those trying to detect treatment (like me) the article is awesome.

I suspect the Magilabs fluorescence unit referred to is the EXA.

I'll drop a note and ask.

Heard back from Dick, yes, it is the EXA.

Currently, I only use the EXA to separate natural & synthetic diamonds and check for oil or resin in emeralds.

The article opens several sapphire doors for my EXA.