De Beers Near Colorless-to-Blue Experimental Gem-Quality Synthetic Diamonds

Abstract

Examination offive small Boron-doped synthetic diamonds, grown by De Beers researchers for experimental purposes, reveals some diagnostic &atures not reported in previous studies of gemquality synthetic diamonds. The presence of internal growth sectors that are blue, yellow, or near colorless has produced faceup colors in three faceted stones that vary fiom near colorless to bluishgreenish gray to blue. Because they look so dzferent fiom previously reported De Beers synthetic diamonds, such faceted synthetics could go unrecognized without carebl gemological testing should they ever become commercially available.Previous articles on gem-quality synthetic diamonds have reported the visible zoning of certain features such as color, ultraviolet luminescence, and graining, and their importance as identification criteria for t h s materd (see Slugley et al., 1986Slugley et al., , 1987Slugley et al., , 1992. Recently, we examined two small crystals (0.12 and 0.20 ct) and three faceted De Beers synthetic diamonds (0.05 to 0.07 ct) that are interesting examples of a lund of internal color zoning that produces a variable overall color appearance (figure 1

Lab-Grown Colored Diamonds From Chatham Created Gems

“…The former contained growth sectors that were blue and colorless, while the latter had sectors that were blue and yellow. Such blue-yellow mixed-type synthetic diamonds have been described before (Shigley et al, 1992;Rooney et al, 1993;Hainschwang and Katrusha, 2003). Figure 14 illustrates how these mixed type IIb+Ib synthetic diamonds can exhibit both blue and yellow colors when viewed face up (they also may display either a grayish or greenish overall appearance depending on the amount of nitrogen impurity present).…”

Synthesis of Diamonds and Their Identification

“…Even blue color can only be achieved by reducing nitrogen concentrations in the diamond to less than 10 18 cm -3 . Otherwise, the resulting material will contain both yellow Type Ib and blue Type IIb growth sectors, which may produce an overall green hue (Shigley et al 1992(Shigley et al , 2004aFritsch and Shigley 1993;Rooney et al 1993;Hainschwang and Katrusha 2003). Both Type IIb or IIa + IIb HPHT diamonds are thus grown by adding a nitrogen getter and a boron dopant (e.g., amorphous boron).…”

“…162. ] due to boron, documented in the literature (Crowningshield 1971;Strong and Chrenko 1971;Koivula and Fryer 1984;Shigley et al 1986Shigley et al , 1987Shigley et al , 1992Shigley et al , 1993aShigley et al , 2002Shigley et al , 2004aBurns et al 1990;Fritsch and Shigley 1993;Rooney et al 1993;Howell et al 2019). Mixed Type Ib + IIb HPHT diamonds may show both yellow and blue color zoning, and may have a green face-up appearance if faceted (Shigley et al 1992(Shigley et al , 2004aFritsch and Shigley 1993;Rooney et al 1993;Hainschwang and Katrusha 2003).…”

Synthetic Gem Materials and Simulants in the 1990s

“…Most synthetic diamonds are yellow, often with brown overtones; the color is associated primarily with the presence of nitrogen. The 1990s saw experimentation with, and limited production of, diamonds with impurities such as nickel and cobalt (Kanda, 1999), as well as boron (Rooney et al, 1993;Reinitz, 1999b). It was also discovered that the typical brownish orange to yellow synthetic diamonds could be treated to create red to brownish red colors (Moses et al, 1993).…”

“…It was also discovered that the typical brownish orange to yellow synthetic diamonds could be treated to create red to brownish red colors (Moses et al, 1993). It is clear, however, that the economic production of near-colorless synthetic diamonds in a size and quality suitable for jewelry was at least one of the goals explored by diamond synthesizers during the last decade (Rooney et al, 1993;Shigley et al, 1997). By 1990, General Electric had demonstrated that they could grow near-colorless type IIa diamonds exceeding 1 ct using a transition-metal flux to prevent the incorporation of nitrogen and boron impurities (Shigley et al, 1993b).…”