Joined: Fri Oct 12, 2007 10:22 pm Posts: 1117 Location: Virginia
Last spring Gemlab reported that they had examined numerous star rubies with lead glass treatment that did not have the "flash effect" typical of lead glass treatment. They concluded that a combination of microscopic examination, radiography and chemical analysis was needed to identify this treatment - and, I suppose, to rule it out.
Are the labs equipped to do these examinations? Are they terrifically expensive?
Can I assume that the star rubies I see at hundreds of dollars a carat have more than heat treatments and that they are"too good to be true?"
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For lead glass usualy you can use reflective light and check for difference of luster on the surface using loup or stereoscope. Bubles can be seen too in some case. I do not think that you need high technology stuff to do the job when you know where and how to look.
Joined: Fri May 12, 2006 11:24 am Posts: 7523 Location: Rome, Italy
hi,
BKK treaters are very smart and, in last years they've improved the filling formula to obtain a drastic reducing of the flash effect. first stones i saw some years ago was full of blue/orangy flames, nowadays they're very hard to see. However gas bubbles are always present, never saw a sample without even a single bubble in and, however, as Olivier pointed out you can easily spot lustre differences between the crystal and the filller playing with reflected light around the stone. Nothing really difficult, you only need a loupe.
ciao
alberto
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