【文章內(nèi)容簡介】 d D through G color grades, and the results were permanent (Moses et al., 1999). Gemological researchers globally mobilized to understand and identify the process (e g. Chalain et al., 1999, 2023。 Schmetzer, 1999。 Collins et al., 2023。 Fisher and Spits, 2023。 Smith et al 2023). ? By late 2023, more than 2,000 decolorized type Ⅱ a HPHTtreated diamonds had been seen at the GIA Laboratory (McClure and Smith, 2023). Today, with several treaters in various countries removing color from diamonds with HPHT annealing, this treatment has bee almost monplace. ? Determining diamond type is central to the detection of colorless to nearcolorless HPHTtreated diamonds. For a thorough review of how diamond type is determined, see Breeding and Shigley (2023). Nearly 99% of all natural gem diamonds are typeⅠ a. Thus far, all colorless to nearcolorless HPHTtreated diamonds reported in the literature have been type Ⅱ a. ? Fortunately, it is easy to determine if a diamond is not a type Ⅱ a by using the DiamondSure (Welbourn et al., 1996), SSEF Type II Diamond Spotter (Boehm, 2023。 Hanni, 2023), or other simple gemological methods (Breeding and Shigley, 2023). At the present time, if a colorless to nearcolorless diamond is not type IIa, then it is not HPHT treated. ? Visual features related to damage caused by the extreme conditions of the treatment may be seen in some colorless to nearcolorless HPHTtreated diamonds. These include a frosted appearance caused by etching or pitting, as well as gray or black graphitization, on naturals or fractures where they e to the surface. ? Such features are not monly observed in untreated colorless type IIa diamonds, although lightly pitted surfaces and graphitized or graphite inclusions have been seen on rare occasions. Therefore, such features are a good indication of treatment, but they are not proof by themselves (Moses et al., 1999。McClure and Smith, 2023。 Gelb and Hall, 2023). ? Because these heat damagerelated features are not always present in a faceted diamond or may be difficult to discern, detection of HPHT treatment in a type IIa diamond generally requires measurement of the absorption and/or photoluminescence (PL) spectra taken with the diamond cooled to a low temperature (see Chalain et al., 1999, 2023。 Collins et al.,2023。 De Weerdt and Van Royen, 2023。 Fisher and Spits, 2023。 Hanni et al., 2023。 Smith et al., 2023。Collins, 2023, 2023。 Novikov et al., 2023。 and Newton, 2023). ? HPHT Treatment to Produce Color. Refinements to HPHT processing have yielded mercial production of a variety of colors in both type I (orangy yellow, yellow, to yellow green) and type Ⅱ (pink or blue) diamonds (Shigley, 2023。 see, ., figure 3). ? Figure 3. This ct Fancy Light grayblue diamond was successfully turned Fancy blue by HPHT treatment. Photos by Elizabeth Schrader. ? Identifying HPHTtreated type la diamonds requires both IR and lowtemperature visiblerange spectroscopy, but several gemological properties offer evidence (see Reinitz et al., 2023). The pink and blue HPHTtreated diamonds initially examined by Hall and Moses (2023, 2023b) ranged from Faint and Very Light to Fancy Intense and Fancy Deep. Lowtemperature PL spectra identified these products. ? As discussed below, bining treatments (., HPHT annealing, irradiation, then lowtemperature heating) can produce interesting results, such as intense pinktored diamonds (Wang et al., 2023b). Smith et al. (2023a,b) contributed useful charts for identifying the natural or treated origin of color in pink and blue diamonds. ? HeatTreated Black Diamond. In the l