This content was first published on IGR – Italian Gemological Review no. 19 in 2024. The information provided here is therefore current as of the original publication date.
In the past months we have seen increased activity in the segment of HPHT treatment of fancy colored diamonds. On several occasions entire parcels of 0.25 to 0.60 ct intensely colored yellow to green yellow diamonds submitted to both the GGTL Liechtenstein and the GGTL Belgium laboratories were identified as HPHT treated.
The situation got currently more worrying, when we detected such HPHT treated diamonds mixed within parcels of melee-sized diamonds, thus far as small as 2 mm. While until recently, the main headache in yellow melee diamonds was the constant pollution with synthetic diamond and rarely irradiated and annealed diamonds, this apparently new trend to HPHT treat really small sizes of type Ia diamond to obtain intense to vivid yellow colors adds a new layer of complexity to our analytical protocol.
The images shown are the FTIR and UV-Vis-NIR spectra of a 3 mm and a 2 mm HPHT treated intensely colored diamond detected at the two labs in the past two months. The curious FTIR showing significant A and B centers combined with several ppm of C centers is highly suspicious by itself. Also, for one stone the fluorescence under roughly SWUV of the DFI system is shown; the distribution and color of the fluorescence is highly suspicious as naturally colored diamonds of such strong saturation are not expected to fluoresce this way.
Article by Thomas Hainschwang [GGTL Liechtenstein Gemlab (Liechtenstein) and GGTL Belgium Gemlab (Belgium)], published on IGR – Italian Gemological Review #19 – Autumn 2024.
