Grading Color in Colored Diamonds Hue, Tone, and Saturation

DDG Ass #11 : Grading Color -With colored diamonds—those outside the normal color range—value is based on the presence of color, and some of the rarest and most valuable colors are saturated pinks, blues, and greens. -In all cases, even a slight variation can have a big impact on value. Hue, Tone and Saturation: -Hue is the first impression of a color, the component that gives color its family identity—the reds, the blues, the greens. -Some hues become less visible as saturation decreases. - Many colors that are commonly called grays are in fact very low saturations of various hues, not pure achromatic grays. -Tone is the degree of darkness or lightness of a color. - Saturation is the strength or intensity of a color. -As saturation levels rise, brownish and grayish components gradually diminish until they’re no longer present. - White, gray, and black aren’t hues because they do not appear on the color spectrum. They’re achromatic, which means “without color.” - Achromatics have no hue, they vary only in darkness, so their gradual progression from white through the neutral grays to black provides an ideal tone scale -Depth of color is the combination of tone and saturation and impacts perception of color. D-to- Z Range: -In the 1950s, GIA established a color grading system for diamonds. -The masterstones set represent known depths of color, ranging from colorless through gradually deepening tints of yellow, or the least amount of color in that range. - Masterstones graded as whole grades, such as H or I, represent the least amount of color in that grade. -Diamonds in the normal color range are judged by their absence of color. -Colored diamonds are graded through the table, in the table-up, or face-up, position. GIA Color Scale: - The GIA Color Scale begins with D (colorless) and continues through the alphabet to Z (light yellow, brown, or gray). -Each letter on the scale represents a narrow color range, not a specific point. And each masterstone marks the highest point—or least amount of color—in that range. - The levels of the GIA Color Scale can be divided into colorless, near-colorless, faint, very light, and light ranges. - Diamonds in the normal color range are graded table-down because subtle color differences are more visible through the pavilion. -D- F color range is so slight they’re almost indistinguishable in diamonds smaller than 0.25 ct. - The G-H-I-J grades are near-colorless. Diamonds with these grades look colorless face-up and nearly colorless face-down. These diamonds are popular because they combine fairly high color with somewhat lower prices. - Diamonds in the K-L-M grades show very faint color face-up and face-down. When mounted, and depending on the type of setting, small stones look colorless but large ones show a slight tint of color. - N through R diamonds appear very light yellow, brown, or gray face-up and face-down, even when they’re mounted in jewelry. -S through Z diamonds are light yellow, brown, or gray. They show substantial color face-up or face-down, loose or mounted. -Once a diamond goes beyond the Z color range, it’s classified as Fancy Light, which causes its price to rise. GIA Color Grading Scale Continued: -Brown diamonds in the D-to-Z range, which are fairly common, are graded with some modifications - Graders describe brown diamonds that are K color or darker with the letter grade and an accompanying colored diamond grade: Faint brown for K to M, Very Light brown for N to R, and Light brown for S to Z. - For Gray stones the colorless to near-colorless range (E to J), they are graded with D-to-Z letter grades. Beginning at K, the grade ranges are the same as for brown diamonds, but their word descriptions consist of only the terms “Faint Gray,” “Very Light Gray,” or “Light Gray.” - Gray diamonds do not receive a colored diamond grading report until they reach a description of Fancy Light, as with yellows and browns. - The difference between one color grade and another on the GIA D-to-Z scale can have a big impact on price. The biggest jump is between the D and E grades. -When creating master stones set for GIA to grade/confirm candidates must meet specific requirements. Trade Terms: - Historically, jewelry professionals often described diamond color using location names as trade terms reflecting on the color of the diamonds that typically emerged from the locations. - Near-colorless diamond “Golconda” because stones from that mining area in India were often near-colorless. - “River” was a term for colorless diamonds, since stones recovered near riverbeds were frequently free of color. -The Jagersfontein mine in South Africa often produced colorless diamonds with blue fluorescence, so diamonds with this appearance were labeled “jagers.” - If a diamond had a yellow tint, it might have been called “cape,” after the Cape of Good Hope in South Africa, an area that yielded mostly yellow diamonds. - There were many variations on the term—top silver cape, silver cape, light cape, cape, dark cape—that depended on the amount of yellow in the individual diamond. - This process is subject to error, Ex :The Premier mine, for example, were frequently light yellow with strong blue fluorescence, the Premier has yielded diamonds in a variety of color ranges -Blue white might be the most misused trade term of all. It has been applied to diamonds from the most colorless all the way to the yellow color range. In the U.S., the Federal Trade Commission (FTC) warns against misuse of the term - The GIA color grading system prevents many of the problems that commonly occur with trade terms. Color Grade Environment: - The grader’s environment must have as little influence as possible on the color grading process. -The most widely available and accepted lighting for color grading diamonds is balanced, daylight-equivalent fluorescent light. -The set of masterstones that a jewelry professional uses should match his or her specific color grading requirements Grading Procedures: - After the proper environment is established, clean the diamond and the masterstones so they’re free of dust and dirt. - To begin, the grader places the diamond table-down to the left of the highest-graded masterstone— -then systematically moves the diamond along the row of masters until it appears to have noticeably less color than the master to its left., then moves the diamond back to the left, placing it to the right of each master until it appears to have less color than one master but more color than the master to its left. -The diamond’s grade will typically be the one associated with the master that has the least amount of color. Ex: if the diamond has less color than the G master but more color than the F master, its grade is likely an F. Master Eye Effect: - When the diamond and the masterstone are very close in color, the side the diamond is on can affect its apparent depth of color. This is an optical illusion called the master-eye effect. Estimate Color Grade -Once set up in the proper environment, the diamond has to be examined both face-down and face-up -Estimation can be fairly accurate, and the process is simple. -With the diamond in the face-down position, the grader looks perpendicular to the pavilion facets. To view the diamond face-up, the grader looks perpendicular to the table. - the face-down position gives the grader the most accurate impression of overall color. Influence on Color: - Factors like unusual proportions, size, and clarity characteristics can influence the appearance of a diamond’s color. -A diamond’s proportions can affect its face-up color, so color grading diamonds with proportions that are very different from the masterstones’ proportions might be challenging. -diamond’s size also affects the visibility of its color - Clarity characteristics like colored inclusions and large cleavages can also affect the appearance of a diamond’s color. When examining a heavily included diamond, a color grader compares the least included area to the corresponding area on the masterstone. Fluorescences: - bout one-third of natural diamonds emit some degree of fluorescence when stimulated by ultraviolet (UV) rays. - GIA Laboratory Diamond Grading Report, the fluorescence entry is a description, not a grade. The terms used to describe fluorescence are None, Faint, Medium, Strong, and Very Strong. - Although it’s rare, some diamonds change color temporarily when exposed to UV radiation. Therefore, it’s important for the grader to evaluate color before determining fluorescence. Grading Colored Diamonds: - Grading colored diamonds is a complex and specialized process. - GIA Colored Diamond Grading System uses reference stones to mark boundaries between color designations, and applies special terms to color ranges. Graders compare stones side by side in a controlled lighting and viewing environment. - Colored diamonds are usually graded in the face-up position, the reason for is that a diamond’s cut can have a noticeable influence on its apparent color. Describing Color: - GIA recognizes just 27 hues for color grading diamonds,Each of the 27 hues represents a range of colors - basic colors like red, blue, and green, and mixed colors like orangy red, green-blue, and greenish yellow with the predominant hue is stated last - GIA uses the following grade terms to describe the combined effect of tone and saturation on the diamond’s hue: Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense, Fancy Dark, Fancy Deep, Fancy Vivid Grading Colored Diamond Process: - Graders begin the process by placing the stone to be graded face-up in a plastic tray inside a viewing box, as a controlled neutral environment - There are obstacles to grading faceted colored diamonds. They tend to present a mosaic of colors, depending on the viewing angle. -Characteristic color this is the diamond’s overall basic color when it’s viewed in the face-up position, which excluding surface reflections, fire, and dark or washed-out areas. -Colored diamond reference stones come in a greater variety of colors than the masterstones used to grade D-to-Z diamonds.