Characteristics of HTHP-Treated Diamonds from Russia

In the paper, the nine HTHP-treated diamond samples from Russia are test by using the micro-examination, FTIR, visible absorption spectrum, low-temperature photoluminescence spectrum and some other methods.The results show that the diamond samples reveal the obvious graphitization, especially the fancy colour diamond samples.The golden yellow, purplish-red, yellowish-green samples are Ⅰ aAB-type;light yellow sample is Ⅰ aB-type and the near colourless samples are Ⅱ a-type.The visible absorption spectra of the samples are very different by the colours.The golden yellow sample reveals the wide absorption band at 475 nm;purplish-red samples reveal the absorption peaks at 638, 614, 595 nm;the yellowish-green samples reveal the absorption peaks at 415, 503 nm and the absorption band at 475 nm;the near colourless samples in the visible region are almost smooth.Besides, the strong luminescent peaks of the samples at 575 nm and 637 nm are observed in the low-temperature(77 K) PL spectra.These characteristics above could provide the foundations for the study on the defects in the crystal lattice and the colouring mechanism of the HTHP-treated diamond.