Color Grading of Colored Diamonds in the GIA Gem Trade Laboratory

King, John T.; Moses, Thomas M.; Shigley, James E.; Liu, Yan

doi:10.5741/gems.30.4.220

Cited by 48 publications

(49 citation statements)

References 10 publications

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“…The study samples covered the entire range of GIA GTL fancy grades, as shown in figure 6. Details of the hue (such as blue in this case), tone (the lightness or darkness of a color), and saturation (the strength of a color) of the diamonds-that is, their location in color space-are described below (again, for details on this color-grading system, see King et al, 1994).…”

Section: Resultsmentioning

confidence: 99%

“…Boron concentrations in natural type IIb diamonds are usually a few ppm at most, and often considerably less than this, so their phosphorescence behavior is similar to that of the lightly boron-doped synthetic diamonds. King et al, 1994). We have continued to look into instrumental measurement to assist in color determinations.…”

Section: Box A: the Physics Of Blue Type Iib Semiconducting Diamondsmentioning

confidence: 99%

“…GIA GTL fancy grades represent a combined effect of tone and saturation (King et al, 1994). Figure 9 images of several blue diamonds superimposed on a chart of the GIA GTL fancy-grade categories.…”

Section: Tone and Saturationmentioning

confidence: 99%

See 2 more Smart Citations

Characterizing Natural-Color Type IIb Blue Diamonds

King¹,

Moses²,

Shigley³

et al. 1998

Gems & Gemology

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Section: Resultsmentioning

confidence: 99%

Section: Box A: the Physics Of Blue Type Iib Semiconducting Diamondsmentioning

confidence: 99%

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Characterizing Natural-Color Type IIb Blue Diamonds

King¹,

Moses²,

Shigley³

et al. 1998

Gems & Gemology

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“…W ostatnich 30 latach wartość rynku aukcyjnego związana ze sprzedażą kamieni szlachetnych wzrosła z 50 milionów dolarów do blisko jednego miliarda (Shor 2013). Do rozwoju rynku kamieni w kolorach fantazyjnych przyczynia się również rozwój systemu oceny takich diamentów (King 1994). Powoduje to porównywalność poszczególnych kamieni i pozwala inwestorowi na wybór najlepszych diamentów do portfela inwestycyjnego.…”

Section: Badania Literaturowe Oraz Charakterystyka Danychunclassified

Diamenty w kolorach fantazyjnych – charakterystyka walorów inwestycyjnych

Potrykus¹

2017

Granice Finansów XXI Wieku. Finanse Publiczne, Rynek Finansowy, Finanse Przedsiębiorstw

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“…On the other hand, retail environments generally provide spot, or point source, lighting (usually with some overall diffuse lighting as well), which accentuates fire (figure 5). Therefore, when we wanted solely to study the effects of brightness, we used dealer-equivalent lighting, which consisted of daylight-equivalent fluorescent lights mounted in fairly deep, neutralgray viewing boxes (e.g., the Macbeth Judge II, as is used for color grading colored diamonds; see King et al, 1994). Similarly, when we wanted to study only the effects of fire, we used our retail-equivalent lighting, which consisted of a series of three halogen lamps mounted 18 inches (about 46 cm) apart and six feet (1.8 m) from the surface of the work table, in a room with neutral gray walls that also had overhead fluorescent light fixtures.…”

Section: G Crown Height) Can Be Calculated From These Eight (A) Almentioning

confidence: 99%

A Foundation for Grading the Overall Cut Quality of Round Brilliant Cut Diamonds

Moses¹,

Johnson²,

Green³

et al. 2004

Gems & Gemology

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GIA began its 15-year study of diamond cut by using a computer to model the way light behaves within a round brilliant cut diamond. From this model, GIA researchers developed proportionbased metrics to predict how diamonds would perform with regard to brilliance and fire. Continued research revealed several important variables that could not be evaluated effectively by computer modeling alone. Thus, the authors asked diamond manufacturers, dealers, retailers, and potential consumers to evaluate brightness (a term selected as more appropriate than brilliance), fire, and overall cut appearance of diamonds representing many different proportion combinations. These observations and discussions confirmed that additional factors, besides brightness and fire, contribute to diamond cut appearance, and that factors in addition to face-up appearance are important in assessing the quality of a diamond's cut. With the trade interactions as a foundation, the authors (1) tested the brightness and fire metrics to find the best fit with human observations, (2) identified and quantified factors in addition to brightness and fire that contribute to face-up appearance, (3) developed a standard viewing environment that mimics common trade environments, (4) created the foundation for a comprehensive diamond cut grading system, and (5) began development of reference software to predict the overall cut grade of a particular diamond. The GIA diamond cut grading system described here includes the components of brightness, fire, scintillation, polish, and symmetry, as well as weight and durability concerns, into a single overall grade for cut quality for standard round brilliants.f the Four Cs (color, clarity, cut, and carat weight), cut is the least understood-and least agreed upon-aspect of diamond appearance. Current claims about the superiority of certain round brilliant diamond cuts focus mostly on three approaches:• The use of specific sets of proportions (e.g., those for the AGS 0, the AGA 1A, "Class 1" cuts [as previously taught by GIA Education], the HRD "Very Good" grades, "Ideal" cuts, and "Tolkowsky" cuts) • The use of viewing devices to see specific patterns or pattern elements in diamonds (e.g., FireScope, Symmetriscope, IdealScope, and various "Hearts-and-Arrows"-style viewers)• The use of proprietary devices, such as the GemEx BrillianceScope and ISEE2, which measure one or more of the following aspects of diamond appearance: brilliance, fire, scintillation, and/or symmetry For GIA's research on the evaluation of diamond cut, we started with a different approach, based on the following questions: What makes a round brilliant cut (RBC, figure 1) proportions create observable distinctions? Which proportion sets produce results that are deemed attractive by most experienced observers? The first stages of our research-which utilized advanced computer modeling-were described briefly by Manson (1991), and then in detail by Hemphill et al. (1998) and Reinitz et al. (2001).Many other groups have used some form of computer modeli...

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Color Grading of Colored Diamonds in the GIA Gem Trade Laboratory

Cited by 48 publications

References 10 publications

Characterizing Natural-Color Type IIb Blue Diamonds

Characterizing Natural-Color Type IIb Blue Diamonds

Diamenty w kolorach fantazyjnych – charakterystyka walorów inwestycyjnych

A Foundation for Grading the Overall Cut Quality of Round Brilliant Cut Diamonds

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