Orange fluor in a greenish/yellow diamond
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I sent half a dozen type II champagne Argyle stones to Prague for HPHT as an experiment a few years back.
I still have 2 and we can not see the cage effect.
Back on topic - no reason your stone would be HPHT, and even if it was there should not be any appreciable price difference.
PS - The 4 people who bought the HPHT stones we have since sold were quite impressed to own them - they were greenish yellow to yellowish greenish and all were jumping out of their skins green/yellow fluoro.
Garry,
indeed, usually IIa HPHT treated diamonds do not reveal "fluorescence cage" for one simple reason. They do not have nitrogen which is the reason of the "cage" fluorescence. However, if an HPHT-treated type IIa diamond contains nickel, the "cage" can be well observed. In any case, however, to detect the "cage" you must provide correct conditions of excitation and observation. Beast of all if you use a good fluorescence microscope liike that described in the Dr. Dobrinet''s paper.
Concerning the price of HPHT diamonds, of course HPHT-treated diamonds are much cheaper that their untreated counterparts. Here in New York, one is happy to sell HPHT treated for 40-30 percent of the price of equivalent untreated stone. You can even buy HPHT diamonds for a price of only 20 percent! of that of the untreated.
indeed, usually IIa HPHT treated diamonds do not reveal "fluorescence cage" for one simple reason. They do not have nitrogen which is the reason of the "cage" fluorescence. However, if an HPHT-treated type IIa diamond contains nickel, the "cage" can be well observed. In any case, however, to detect the "cage" you must provide correct conditions of excitation and observation. Beast of all if you use a good fluorescence microscope liike that described in the Dr. Dobrinet''s paper.
Concerning the price of HPHT diamonds, of course HPHT-treated diamonds are much cheaper that their untreated counterparts. Here in New York, one is happy to sell HPHT treated for 40-30 percent of the price of equivalent untreated stone. You can even buy HPHT diamonds for a price of only 20 percent! of that of the untreated.
adamasgem
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Dr Zaitsev..
Are you referring to treated natural Argyle material with regard to the IIa statement or nickel catalyst IIa synthetics?
How deep does it appear the higher surface concentration of the luminescent centers go, and would there be any difference between the depth of nitrogen related centers and nickel related centers in the HPHT treated stones?
Could you also please comment on http://www.adamasgem.org/typeiia.html (which you may or may not have seen), with regards to the spectrum shift we documented, which was the first "off label" use of the DiamondView.
Marty,
these are my comments:
Q: Are you referring to treated natural Argyle material with regard to the IIa statement or nickel catalyst IIa synthetics?
A: I mean Ni and N impurities, which can be present in any diamond, natural or synthetic.
Q: How deep does it appear the higher surface concentration of the luminescent centers go, and would there be any difference between the depth of nitrogen related centers and nickel related centers in the HPHT treated stones?
A: Sorry!!! That was a mistake! The reason of the "cage" is not the enhanced concentration of fluorescence centers at the facet junctions, but a specific light scattering inside HPHT-treated diamond, which concentrate luminescence at the edges. I do not know yet the mechanism of this scattering. Very tentatively, it might be due to the A-aggregares of nitrogen.
Q: Could you also please comment on http://www.adamasgem.org/typeiia.html (which you may or may not have seen), with regards to the spectrum shift we documented, which was the first "off label" use of the DiamondView.
A: Thank you for giving me this link! I did not see it before. It is an interesting observation. What you see in the luminescence spectra It is not a shift, but a redistribution of intensities of different components constituing the A-band. The origin of the A-band is, most probably, optical centers decorating dislocations and the dislocation cores themselves. The broad-band spectrum of the A-band results from strong nonhomegenous broadening due to mechanical stress developed around dislocations. Two main components of the A-band are 440 nm band and 500 nm band. I do not know what is the physical difference between them. The change in the intensities of these bands (and may be in their widths) imply that the 440 nm band is more stable than the 500 nm band. Or may be the 430 nm band is enhanced by the HPHT treatment? Anyway it is a valuable observation, which could help in recognition of HPHT-treated diamonds.
Concerning the GR1 center, sorry!, I have to tell you, that there is NO GR1 center in the VIS absorption spectra I saw in your report. The change of the slope is not the indication of the GR1 center. If you would see even slightest traces of the GR1 center in VIS absorption, you must excite GR1 center very effectively in luminescence., what is not the case for the PL spectra I see in your report.
Concerning HPHT and slight irradiation to hide the treatment, of course, is is done by many. I saw and examined such stones myself and some of these stones were sertified by reputable gem labs as "natural untreated"! However, I do not blame them, indeed to recognize treatment in those stones you must be a really experienced scientist and have access to top level spectroscopic equipment.
Regards,
these are my comments:
Q: Are you referring to treated natural Argyle material with regard to the IIa statement or nickel catalyst IIa synthetics?
A: I mean Ni and N impurities, which can be present in any diamond, natural or synthetic.
Q: How deep does it appear the higher surface concentration of the luminescent centers go, and would there be any difference between the depth of nitrogen related centers and nickel related centers in the HPHT treated stones?
A: Sorry!!! That was a mistake! The reason of the "cage" is not the enhanced concentration of fluorescence centers at the facet junctions, but a specific light scattering inside HPHT-treated diamond, which concentrate luminescence at the edges. I do not know yet the mechanism of this scattering. Very tentatively, it might be due to the A-aggregares of nitrogen.
Q: Could you also please comment on http://www.adamasgem.org/typeiia.html (which you may or may not have seen), with regards to the spectrum shift we documented, which was the first "off label" use of the DiamondView.
A: Thank you for giving me this link! I did not see it before. It is an interesting observation. What you see in the luminescence spectra It is not a shift, but a redistribution of intensities of different components constituing the A-band. The origin of the A-band is, most probably, optical centers decorating dislocations and the dislocation cores themselves. The broad-band spectrum of the A-band results from strong nonhomegenous broadening due to mechanical stress developed around dislocations. Two main components of the A-band are 440 nm band and 500 nm band. I do not know what is the physical difference between them. The change in the intensities of these bands (and may be in their widths) imply that the 440 nm band is more stable than the 500 nm band. Or may be the 430 nm band is enhanced by the HPHT treatment? Anyway it is a valuable observation, which could help in recognition of HPHT-treated diamonds.
Concerning the GR1 center, sorry!, I have to tell you, that there is NO GR1 center in the VIS absorption spectra I saw in your report. The change of the slope is not the indication of the GR1 center. If you would see even slightest traces of the GR1 center in VIS absorption, you must excite GR1 center very effectively in luminescence., what is not the case for the PL spectra I see in your report.
Concerning HPHT and slight irradiation to hide the treatment, of course, is is done by many. I saw and examined such stones myself and some of these stones were sertified by reputable gem labs as "natural untreated"! However, I do not blame them, indeed to recognize treatment in those stones you must be a really experienced scientist and have access to top level spectroscopic equipment.
Regards,
adamasgem
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adamasgem
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adamasgem
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Alex, based on tests when the PO started irradiating the mails post the Anthrax episodes, we noticed a change in slope at 741nm in the vis spectra post E beam irradiation, which is consistent with the start of permanent broad band radiation damage, and there fore I attributed it to GR1 damage, what you see in greens and irradiated yellows. Maybe I'm not technically correct in that it is not the GR1 "center", but the broad band radiation (GR1 system) damage. I'm not the physicist, but it a reliable indicator with the SAS2000 that you see in irradiated yellows, greens and even in colorless material. I don't see where it could be related to anything else.
Personally, I don't think the physicists see it in colorless material because of their generally looking at things in absorbance mode rather than transmittance mode. I have curve fit tests in the SAS2000 software for both this change in slope for radiation damage as well as for SOME fracture filling types (at 765nm).
adamasgem
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adamasgem
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Alex, I forgot to thank you for the observation comments as to what is happening. It is the FIRST time we have seen a reasonable explanation.
At the time DeBeers and later all the major labs (around 2000 or so) were made aware of the findings, and DeBeers was uncooperative (and I mean very uncooperative) , and would not try to duplicate the results we found, supposedly, as I remember, because of funding. At GIA, I think it was the typical not invented here syndrome and I think they were relying on the existance of a 741nm in PL to "show" that it was "natural IIa, but of course anyone with a little background knew that even though this signature was destroyed by HPHT, it could be easily introduced by llow level radiation. Or at least, DeBeers (or GIA) would never disclose that they tried. I think they did not like the off label use of the DiamondView or their not released dual laser HPHT Raman system (based on 575/637 ratio and existance of a 741) got in the way (sic).
Because of no money and not having $10K or more to throw at the problem, I used 218nm band-pass filters with two 20 watt deuterium bulbs powered by Ebay bought Hamamatsu supplys, and got very weak signal patterns, but consistent with the higher power DiamondView (I believe 2 100watt filtered Xenons). Still cost me $1K by the time I got filters and cables and bulbs. Owen Bordelon (of AGTA) even built me a variable Deterium supply so that I could experiment with bulbs bought on the cheap, instad of $450 apiece. One of the additional problems is the very low throughput of the commercially available 218nm band pass filters, on the order of 8 to 15% in the spectral range desired, which I understand was also a problem for DeBeers.
Sorry for Hi-Jacking the thread, Pricescopers, but it is important, and there are very few out there with the requisite knowledge and background in the subject willing to contribute.
adamasgem
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Alex, scattering concentration doesn''t make any sense, to me at least, otherwise you''d see it in the same cuts, no matter what the repolishing as the color change and HPHT induced yellow green fluorescence is apparently homogeneous. Think of the diffusion treated sapphire analogy. Just an opinion. Surface concentration makes a better arguement. You could prove that thesis by deeply recutting only half of a stone that showed the cage effect, and see if the cage effect on the lightly repolished stone is still there.
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