The Australian Gemmologist has just published a comprehensive article on these treated gems from the team at the Gem and Jewelry Institute of Thailand. You can see it online at this link:
Post subject: Re: Cobalt-doped glass-filled sapphires
Posted: Fri May 24, 2013 3:58 pm
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Joined: Thu Dec 13, 2007 3:42 pm Posts: 4091 Location: the Netherlands
Hey Dick,
one line got me thinking...
Quote:
But more importantly, all of the stones tested showed a strong red to orange-red when viewed with the Chelsea filter. Both natural and synthetic blue sapphires show no red.
I've come across a synthetic sapphire (which I don't have here at the moment, of course ) that fluoresced red in high intensity halogen light. What could be the chromophore there?
Attachment:
Cobaltdopedsapphire.jpg [ 179.34 KiB | Viewed 2733 times ]
I thought it was cobalt back then cause cobalt doped spinel does this too but I now have learned that cobalt isn't on John E's list of possible chromophores in sapphire... or is it?
Post subject: Re: Cobalt-doped glass-filled sapphires
Posted: Sat May 25, 2013 7:50 am
Valued Contributor
Joined: Tue Mar 13, 2007 11:12 am Posts: 484 Location: Chiang Rai Thailand
Great article with very good identifying techniques covered. It appears that Barbra's favorite gemological tool, the Chelsea filter, is one of the main tools to carry when shopping for Sapphire now. Ted Themellis contacted me several months ago about this treatment as he was doing some research on how fast it was spreading around. I reported that I have not found them yet at the Burmese border, however, it is only a matter of time. Best regards, Lee
Post subject: Re: Cobalt-doped glass-filled sapphires
Posted: Sat May 25, 2013 3:08 pm
Platinum Member
Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
Tim wrote:
I've come across a synthetic sapphire (which I don't have here at the moment, of course ) that fluoresced red in high intensity halogen light. What could be the chromophore there?
Post subject: Re: Cobalt-doped glass-filled sapphires
Posted: Mon May 27, 2013 4:33 pm
Moderator
Joined: Thu Dec 13, 2007 3:42 pm Posts: 4091 Location: the Netherlands
No idea, Rick, a bit of chromium would be a possibility. I briefly looked at it today, one of my students stuck it in a ring, no sign of a cobalt spectrum.
So a rectumfication on that other thread: that wasn't a cobalt doped sapphire... they don't exist. (deleted the remark in question in that thread).
Back on subject... Here is a shot of air bubbles in a cobalt-doped glass filled sapphire. You can also see the color is in patches and streaks where the glass filling is present. The stone is a cabochon of around three carats.
Forgot to mention, the stone is very nicely red if looked upon through the Chelsea Filter.
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