![]() As discussed in our 2013 article, most diamonds also contain lattice defects which, in sufficient concentrations, can produce selective absorption of incident light. There are, however, intrinsic absorption features in the spectra of all actual diamonds. GIA’s laboratory staff, which has the opportunity to examine a large number of colored diamonds, faces this identification challenge on a daily basis.Ī theoretically pure and defect-free diamond would be completely colorless, and a unique attribute would be its transparency (or lack of light absorption) across a wide portion of the electromagnetic spectrum from the ultraviolet through the visible and into the infrared regions. It also discussed how spectroscopy techniques, used to detect absorption and/or emission bands caused by those optical defects, play a leading role in making this important determination. The brief article that accompanied the chart discussed the ongoing challenge presented by the identification of natural, treated, and synthetic diamonds. The chart presented some basic information on those defects, including the ones responsible for the colors and ultraviolet fluorescence reactions of most diamonds. In 2013, the authors published a simple chart listing the major optical defects that can occur at the atomic lattice level in diamond (Shigley and Breeding, 2013). The chart shows how similar diamond colors can result from different light absorption patterns. A chart has been prepared to illustrate the visible spectra of various colored diamonds as recorded at low (liquid-nitrogen) temperatures with a spectrophotometer. Yet the broader regions of absorption, which can be difficult to observe with the spectroscope, often have a greater influence on a diamond’s color. The spectroscope allows a gemologist to observe some of the more intense and narrower absorptions in the visible spectrum of diamond as dark bands at specific wavelengths. ![]() The unabsorbed portion of this light is transmitted through the diamond and is interpreted by the human vision system as the perceived color. Applied Jewelry Professional ™ Online Diplomaĭiamond color is usually the result of selective absorption of incident white light.
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