how would heat treatment affect a cornflower blue sapphire??

[upgrading mama]

I have done a quick search here about heat treatment, without finding the answer to this question.

Does heat treatment wear off? If so, how long, generally would that take?
can the stone be reheated (or microwaved

) haha couldn''t help it...

Seriously though, should I not buy a stone that has been heated?

 

[C Smith]

Heating sapphire is a permanent change in color.Indeed, most blue sapphire and blue topaz is heated in todays market. Heat in the ground is a naturally occuring color enhancer so artificial heating is often seen as an extension of a natural process by some. Zircon is the only stone I know of that will revert back to original coloring from heated condition on occasion(there may be others...perhaps someone else will chime in?).

 

[Richard M.]

Date: 6/23/2006 5:30:42 PM
Author:Sophie
I have done a quick search here about heat treatment, without finding the answer to this question.


Does heat treatment wear off? If so, how long, generally would that take?

can the stone be reheated (or microwaved

) haha couldn''t help it...


Seriously though, should I not buy a stone that has been heated?

What stone are you concerned about? You needn''t worry about color fading in heated sapphires, rubies, tanzanites, tourmalines, citrine quartz or aquamarines. If you''re thinking about sapphire/ruby, there are much larger questions involving beryllium diffusion which involves heat but is not what I would call "standard" heat treatment. Beryllium bulk diffusion (considered undesirable because it introduces a non-native element into the stone) is mostly seen in yellow, brown, orange and padparadscha colors. There are currently questions about beryllium treatments to lighten dark blue sapphires but definite results are not in yet.

As a matter of interest, some unheated stones including kunzite and some types of topaz will fade when exposed to sunlight. It''s a complex topic. And I''ve actually heard of microwaves and toaster ovens being used to heat-treat some gems!

Richard M.

 

[Richard M.]

After posting I finally noticed your headline about "cornflower blue sapphire." Sapphires have been heated to improve color for at least 50 years I know of, and probably longer. The treatment is permanent.

Whether you buy a heated sapphire is mainly a question of what you like, what you can afford, and how concerned you are about having a totally natural gem. Certificated unheated cornflower blue sapphires are a lot more expensive than the heated variety.

As to beryllium-diffused blue sapphires, the labs are still arguing about whether they''re even on the market. Some think the beryllium may come from heating in ovens previously used to diffuse non-blue stones; others have detected beryllium in blue sapphires known to be natural and not treated in any way. And some are saying beryllium stones are definitely on the market. That ball of twine has a way to unwind yet.

Richard M.

 

[upgrading mama]

thanks guys for the info, it truly was helpful. I am not looking at one in particular, but I as I browse sites I sometimes see this, and wondered if it would be permanent or not, in the event I was interested in one.