Post subject: Diamond classification - the diamond types
Posted: Sat Jan 30, 2016 12:25 am
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Joined: Sun Oct 16, 2005 12:22 pm Posts: 21600 Location: San Francisco
I just received a preview of this excellent article on the detection of diamond types using FTIR spectroscopy. A must read! Question Alberto and Mikko: Once we identify the diamond type of an unknown using the FTIR can we also positively determine HPHT treatment or synthetic origin? [pdfview]http://www.gemmoraman.com/Portals/0/Documents/DiamondType.pdf[/pdfview]
Post subject: Re: Diamond classification - the diamond types
Posted: Fri Feb 12, 2016 6:14 am
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Joined: Fri May 12, 2006 11:24 am Posts: 7523 Location: Rome, Italy
Barbra Voltaire wrote:
I just received a preview of this excellent article on the detection of diamond types using FTIR spectroscopy. A must read! Question Alberto and Mikko: Once we identify the diamond type of an unknown using the FTIR can we also positively determine HPHT treatment or synthetic origin? [pdfview]http://www.gemmoraman.com/Portals/0/Documents/DiamondType.pdf[/pdfview]
Thank you for the compliments, Barbra . and sorry for the very late reply we just get back from Tucson and just started dealing with all the work accumulated on the desk during our absence... . about your question, there is not a simple and direct answer to that, unfortunately. Knowing the exact diamond type is a huge step towards the identification of possible treated and synthetic stones and, of course FTIR is obviously THE tool. the spectrum can provide for additional information as an example, some minor boron presence in IIa as seen in fig 8 (vast majority of HPHT synthetics) and other specific peaks coming from defects typical of some CVD production but, in many cases, its a combination of multiple techniques that can solve the issue. Even PL alone in many cases is able to spot for the HPHT treatment as described in a previously released application note ( http://www.gemmoraman.com/Articles/HPHT.aspx ) but, there are limitations even here, in some HPHT treated the presence of PL features is missing even in liquid nitrogen immersion. That said, given that >95% of colorless to near colorless stones are high nitrogen type IaAB, those cannot be synthetic or HPHT-treated and, in the end, as for many other aspects of Gemology, the combination of multiple techniques is the only way to be relatively sure about what we are dealing with....
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