A Defect Study and Classification of Brown Diamonds with Deformation-Related Color

Abstract

For this study, the properties of a large sample of various types of brown diamonds with a deformation-related (referred to as “DR” in this work) color were studied to properly characterize and classify such diamonds, and to compare them to pink to purple to red diamonds. The acquisition of low temperature NIR spectra for a large range of brown diamonds and photoexcitation studies combined with various treatment experiments have opened new windows into certain defect characteristics of brown diamonds, such as the amber centers and naturally occurring H1b and H1c centers. It was determined that the amber centers (referred to as “AC” in this work) exhibit rather variable behaviors to annealing and photoexcitation; the annealing temperature of these defects were determined to range from 1150 to >1850 °C and it was found that the 4063 cm−1 AC was the precursor defect of many other ACs. It is suggested that the amber centers in diamonds that contain at least some C centers are essentially identical to the ones seen in diamonds without C centers, but that they likely have a negative charge. The study of the naturally occurring H1b and H1c link them to the amber centers, specifically to the one at 4063 cm−1. Annealing experiments have shown that the H1b and H1c defects and the 4063 cm−1 AC were in line with each other. The obvious links between these defects points towards our suggestion that the H1b and H1c defects are standalone defects that consist of multiple vacancies and nitrogen and that they are—in the case of brown diamonds—a side product of the AC formation. A new classification of DR brown diamonds was elaborated that separates the diamonds in six different classes, depending on type and AC. This classification had been completed recently with the classification of brown diamonds with a non-deformation-related color (referred to as “NDR”), giving a total of 11 classes of brown diamonds.

Diamonds from the Mir Pipe (Yakutia): Spectroscopic Features and Annealing Studies

“…At the same time, the H3 system decreased and the H4 system, along with the 613 nm system, disappeared. The annealing temperature of the 613 nm system accorded with the published works [41,45,46]. The 490.7 nm center fell drastically as a result of annealing at 1500 • C and annealed out completely as a result of annealing at 1700 • C; this reflects the thermally activated diffusion of dislocations (Figure 6).…”

Gemological Characteristic Difference between Colorless CVD Synthetic Diamonds and Natural Diamonds

“…Both natural diamonds and CVD synthetic diamonds have the same refractive index, density, and appearance, and they have no distinct difference under a microscope. Obvious internal defects and stress lines might appear during the growth of natural diamonds due to the changes in external conditions [ 17 , 18 , 19 ].…”

Structural peculiarities, mineral inclusions, and point defects in yakutites—A variety of impact‐related diamond

“…Initial assignment of this band to dislocationrelated defects (Plotnikova et al, 1980) found some support in Mora et al (2002Mora et al ( , 2003. In a recent detailed investigation of PL spectra of deformed N-containing terrestrial diamonds (Hainschwang et al, 2020) it was suggested that the "700" nm band is a vibronic mode of a ZPL located at 620 nm, which, in turn, is clearly pronounced only at low temperatures. Whether the "700 nm" band from the later paper corresponds to features observed in yakutite or not is yet unknown, but in any case, its dislocation-related origin seems to be plausible.…”