The stone I tested was Type IIb diamond, its boron peaks were positions at 1290, 2456, 2802, 2930, 4090cm-1, DiamondView test showed mosaic pattern which was typical natural Type II diamond’s characteristic. The one didn’t show any phosphorescence. One thing confused me was about the PL test (under LN), it revealed small peak at 741nm which could produce by natural and artificial irradiation. I have experienced some blue diamonds certified by GIA, small peak at PL 741nm were also found.
I have learned it is not uncommon to treat natural brownish type IIb to make them nice blue. Any signs of HPHT treatment in the PL spectrum? I would have it FTIR tested. Images of PL spectrum and the stone?
This blue diamond was confirmed natural diamond already, not synthetic either CVD or HPHT. Just doubted about the PL 741nm, a small peak was shown, could it be radiated or natural blue color?
Joined: Wed Oct 22, 2008 5:00 am Posts: 344 Location: Finland
Many natural type IIb stones exhibit a small GR1-peak at 741nm, so no worry. The name of the band is "general radiation", but irradiation is not the only cause for it. In case of natural IIa & IIb the reason is plastic deformation. This peak is destroyed in HPHT-treatment, so I expect to see it in natural untreated type IIb stone. However, it is technically possible to post-irradiate the stone with minor dose for recreating the peak. I have only seen this done for IIa, but see no reason why it wouldn't work for IIb as well.
Joined: Mon Aug 20, 2012 11:32 pm Posts: 1747 Location: Florida, United States
Conny Forsberg wrote:
I have learned it is not uncommon to treat natural brownish type IIb to make them nice blue. Any signs of HPHT treatment in the PL spectrum? I would have it FTIR tested. Images of PL spectrum and the stone?
I have never seen a type 2b diamond exhibit a brown color. Perhaps you are thinking of type 2a?
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