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"AGL Discovers Heated Sapphires with Unstable Color Centers"

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icy_jade

Ideal_Rock
Joined
May 1, 2009
Messages
2,919
Thanks for sharing.

I actually recall my jeweller mentioning that yellows and pads are generally not color stable. Seems like a known thing in trade? Does anyone know?
 

Rfisher

Brilliant_Rock
Premium
Joined
Oct 19, 2013
Messages
1,616
Thanks for sharing.

I actually recall my jeweller mentioning that yellows and pads are generally not color stable. Seems like a known thing in trade? Does anyone know?
I would take that to mean the jeweler knew those stones he’s talking about are non-stable treated.
The fading is not a thing with natural colored stones, right?!?
 

icy_jade

Ideal_Rock
Joined
May 1, 2009
Messages
2,919
I would take that to mean the jeweler knew those stones he’s talking about are non-stable treated.
The fading is not a thing with natural colored stones, right?!?
Natural. He wasn’t referring to treated. He mentioned it fairly casually like it’s a well known thing. The conversation actually started with me asking about unstable yellows (not heated) that faded after being kept in safe that I’d heard from another jeweller, and then he mentioned that pads colors can also fade if you keep in safe. But just need to wear under sun periodically and the color will return.
 

icy_jade

Ideal_Rock
Joined
May 1, 2009
Messages
2,919
@Rfisher @elle_71125 I know right? I was like - but pads are soooo expensive??? But he just shrugged and said it’s common.

You can do a color stability test at most labs I think. My yellow sapphire was assessed for color stability at two labs and I wouldn’t have bought if it wasn’t certified.
 

PieAreSquared

Shiny_Rock
Joined
Dec 18, 2014
Messages
168
The "Release" from AGL looks like a giant infomercial to me -"Be afraid, and send us another $50 or else the standard report we just charged you for is worthless'.

After reading this post, I kept thinking I had already heard about this somewhere else a while ago...

Sure enough, the unstable color of some orangey-pink sapphires was reported at least a year before AGL's amazing "discovery", and confirmed by the truly world-renowned Swiss Gemmological Institute SSEF.
The 'tenebrescence' or reversible photochromism, of some yellow sapphires was reported by the same institute way back in 1997...

If you really want to geek out, read the original article here:
https://gem-a.com/images/JoG/JoG2018_36_4.pdf
 

voce

Ideal_Rock
Joined
May 13, 2018
Messages
2,216
I wonder if this same problem affects pad spinel. There are no yellow spinels, but plenty of pink and orange and orangey-pink.
 

MissyBeaucoup

Brilliant_Rock
Premium
Joined
Mar 10, 2017
Messages
910
Brad at the Gem Trader occasionally has some hackmanite for sale. This is a stone that is collectible partly because it has such strong tenebrescence. If anybody has some, please post pictures.

This is a photo of Brad’s that I saved. It shows hackmanite before, during, and after exposure to SWUV light. (I would have bought it but I only have a LWUV light. You do need eye protection to use SWUV, but that’s a good point that it could be contained in sunlight.)

Anyway, tenebrescence 7189FE49-9EED-4A7A-A9E5-499DE4B81BD4.gif is super cool! I understand someone being disappointed if their sapphire turned a less pretty color though.
 

icy_jade

Ideal_Rock
Joined
May 1, 2009
Messages
2,919
Brad at the Gem Trader occasionally has some hackmanite for sale. This is a stone that is collectible partly because it has such strong tenebrescence. If anybody has some, please post pictures.

This is a photo of Brad’s that I saved. It shows hackmanite before, during, and after exposure to SWUV light. (I would have bought it but I only have a LWUV light. You do need eye protection to use SWUV, but that’s a good point that it could be contained in sunlight.)

Anyway, tenebrescence 7189FE49-9EED-4A7A-A9E5-499DE4B81BD4.gif is super cool! I understand someone being disappointed if their sapphire turned a less pretty color though.
Here you go. Not mine but came across them some time ago and found it quite interesting as well. Beautiful color change


And

 

Anne111

Shiny_Rock
Joined
Nov 30, 2017
Messages
320
Now I'm totally confused. Does this mean we can now buy only completely unheated stones to be 100% sure they are really untreated, except oiling? WT... is going on???

This whole treatment issue is driving me nuts!!!!!!!!!!!!!!!!!!!

Could we start a list with vendors who sell only gems whose treatment-statement can be trusted based on the type of lab reports they provide?

Aside the 'recommended vendor list':
'Recommended vendors with verified or correctly disclosed treatments'? or something of the kind?
That would thin the currently too long list and give those who care about treatments a better place to start.

A sample of somebody NOT on that list would be a new UK-Indian website with hundreds of interesting sapphires/rubies whom I asked to tell me about the treatment of a specific gem (they didn't give any data in their online presentation at all, only "Grade AA") and the answer was.... 'silence'. How can we be expected to buy from anybody if the value of a sapphire/ruby etc. could be $100 or $1000 depending on treatments which we cannot know in te end?
 

icy_jade

Ideal_Rock
Joined
May 1, 2009
Messages
2,919
Now I'm totally confused. Does this mean we can now buy only completely unheated stones to be 100% sure they are really untreated, except oiling? WT... is going on???

This whole treatment issue is driving me nuts!!!!!!!!!!!!!!!!!!!

Could we start a list with vendors who sell only gems whose treatment-statement can be trusted based on the type of lab reports they provide?

Aside the 'recommended vendor list':
'Recommended vendors with verified or correctly disclosed treatments'? or something of the kind?
That would thin the currently too long list and give those who care about treatments a better place to start.

A sample of somebody NOT on that list would be a new UK-Indian website with hundreds of interesting sapphires/rubies whom I asked to tell me about the treatment of a specific gem (they didn't give any data in their online presentation at all, only "Grade AA") and the answer was.... 'silence'. How can we be expected to buy from anybody if the value of a sapphire/ruby etc. could be $100 or $1000 depending on treatments which we cannot know in te end?
Huh? As far as I understand, untreated yellow and pad sapphires can also have unstable colors, just like heated ones. Key is to check for color stability.

Buying from the trusted vendor list doesn’t guarantee you get a color stable stone as far as I’m aware. Get a decent lab to certify the stone before you buy. The color stability test doesn’t require expensive fancy equipment but does run the risk of an unstable stone changing color so if a vendor isn’t willing to get the test done, I’ll be wary too.
 

voce

Ideal_Rock
Joined
May 13, 2018
Messages
2,216
is that so? What makes them unstable?
Interactions between UV spectrum photons and the band gap potential of electrons in elements within the crystal structure of the sapphire. It probably requires understanding of materials science to really understand this.

As far back as 1987, there were seven types of yellow sapphires identified, each with a different color center. See this article from Gems and Gemology, Winter 1987.

I also came across this article from James Allen and thought it interesting and much less technical.
 

icy_jade

Ideal_Rock
Joined
May 1, 2009
Messages
2,919

Anne111

Shiny_Rock
Joined
Nov 30, 2017
Messages
320
Thanks. Just to be clear: An unheated padparadscha or yellow sapphire would come up as 'color unstable' in a standard testing process at the high-end labs?
 

icy_jade

Ideal_Rock
Joined
May 1, 2009
Messages
2,919
Thanks. Just to be clear: An unheated padparadscha or yellow sapphire would come up as 'color unstable' in a standard testing process at the high-end labs?
Possible but not always. There are color stable pads and yellow sapphires just as there are non-color stable ones. So best to check if you are in the market for a pad or yellow sapphire. If you get from a reputable vendor he/she should know. If not then ask for a cert from a decent lab that has/will perform the color stability test
 

ChaiK

Brilliant_Rock
Joined
Jun 8, 2018
Messages
847
Possible but not always. There are color stable pads and yellow sapphires just as there are non-color stable ones. So best to check if you are in the market for a pad or yellow sapphire. If you get from a reputable vendor he/she should know. If not then ask for a cert from a decent lab that has/will perform the color stability test

Or a pink sapphire. Testing is good.
 

kindred

Brilliant_Rock
Premium
Joined
Dec 3, 2008
Messages
919
I can't figure out how to quote, but I have the same question as @voce. I am about to buy a pink/red/orange spinel and before I spend thousands of dollars on one I'd like to know if spinels can have the same problem. :eek-2:
 
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