Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond) Al Gilbertson, GG (GIA), CG (AGS)

Gem Ma rket N ews Feature Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond) Al Gilbertson, GG (GIA), CG (AGS) In this comprehensive article, the author discusses the mixing dichroic colors, the cutter has failed miserably. value factors of colored gems in five parts. This article Josh Hall (Vice President, Pala International, Inc.) looks at the first two parts. Future issues of the Gem helps us put cut in perspective to a gem’s value (from Market News will continue the discussion, looking at Hall’s personal comments—see Fig. 1-1). He states other factors. that color is about 60% of the gem’s value, followed by the location it comes from which can influence 15% of Part 1: Value Factors of Colored Gemstones the value (this can be much more for certain origins, For our purposes, the word “cut” means more than just such as Kashmir sapphire). After that, cut and size the shape of a gem; it also encompasses the elements of each represent around 10% of the value followed by “cut quality.” Cut quality refers to how well the gem was the shape (outline) of the gem. I’m going to add clari - manufactured, or how well ty and color zoning to the various facets were placed. discussion below. Each of Combined with the propor - these can be quite variable. tions, symmetry, and polish, Before we go through a well-cut gem should have each of the value factors in a beauty that not only comes Figure 1-1, it is important from its color and clarity, but to note that the relative from how the facets interact value percentages represent with light. This series should Josh’s experience, but there illustrate how to assess the are always exceptions. For elements of cutting, and how example, in some local to better understand the retail markets, size and cut impact of cut quality on the can embody more than 10% value of various gems. Part of the gem’s value. Certain Fig. 1-1. Illustration by Al Gilbertson, © GIA. of that will include under - size ranges and cut qualities standing the choices a cutter can be perceived as more makes and why. While our focus is on forms of faceted saleable, so a premium can be added. All of these fac - gems, we will briefly touch on non-faceted gems. tors are discussed on a basic level. In reality, many are The quality of the rough material limits the gem - more complicated for each particular gem material. stone’s final appearance. Therefore cutters prefer rough that is transparent and without many inclusions. Some Color is King! gems are rarely eye-clean, so some inclusions become In color science, there are three dimensions to color: hue acceptable in those materials. Since color is the highest (red, green, blue, etc.), saturation (intensity or richness priority for colored gems, how a cutter manages the of a color), and tone (lightness or darkness). There is a light as it enters and exits a gem becomes an exercise fourth color factor for gemstones: uniformity of color . in artistry. Ruby rough with a deeply saturated red Our eyes see color as seven colors of the rainbow: red, color and free from even minor inclusions under 10X orange, yellow, green, blue, indigo, and violet. Each of will produce gems of noteworthy face-up color and these colors is made of rays of light, each traveling at dif - appearance, even if the fashioning is poor. But if the ferent speeds with different wavelengths. When all of the faceting washes out the color or muddies its color by above colors combine, we see it as white light. When The GemGuide Value Factors of Colored Gemstones January/February 2016 u 1 gle pure hue. For example, evenly blue sapphires have more value than those with secondary green hues. For a colored stone (non-diamond), color is the most impor - tant factor in determining quality. Country of Origin For many colored gems, the country of origin , or the mining location, greatly affects the value (see Fig. 1-3). For example, this is truer and more extreme for an untreated sapphire of intense blue color from Kashmir which is worth far more than a similar sapphire mined elsewhere. A few of the major grading labs have the equipment and expertise to determine geographic origin. An origin report from one of these labs is required in validating the gem’s value when highly regarded loca - tions can significantly increase the stone’s price (more than the 15% in a couple of cases). Fig. 1-2. Illustration by Al Gilbertson, © GIA. Row 1: spo - Be cautious and read the report from a lab thorough - dumene, sapphire, scheelite, sphalerite, tourmaline. Row 2: ly. A standard report usually identifies the gem material, sapphire, sapphire, spinel, euclase, spinel. Photos by Robert but not the geographic origin. Language used in a stan - Weldon, © GIA. dard GIA Identification Report for a copper-bearing tourmaline will state, “This copper and manganese bear - white light enters a colored gem, part of the light can be ing tourmaline may be called ‘paraíba’ tourmaline in the absorbed. For instance, if a gemstone absorbs all of the trade. The trade term ‘paraíba’ comes from the Brazilian colors except blue, only the blue will be visible, and we locality where this gem was first mined, however, today see the gemstone as blue. it may come from several localities.” The trade calls The optimal color range (combination of hue, satu - these Paraíba tourmalines even though the location is not ration, and tone) for each gem is different, and for from Brazil. Only if the gem was sent in for a country of many gems, availability in the optimal color can be origin report, will it indicate the country, such as Brazil. scarcer (see Fig. 1-2). Pale colors usually have a rela - In that case the price will be impacted by the Brazil ori - tively low value. However, pale blue-green (or mint) gin. tourmaline from Afghanistan/Pakistan commands high Ruby, sapphire, red spinel, emerald, and Paraíba prices, much higher than their more saturated counter - tourmaline all qualify for a GIA Colored Stone parts from the same source. Identification & Origin Report. However, that does not Wayne Emery ( The Gem Cutter ) points out that some mean GIA will be able to determine a country of ori - retailers have learned that there are customers who pre - gin in every instance. GIA determines geographic ori - fer less saturated stones because they appear to be gin by collecting chemistry and spectroscopic data, brighter and have more sparkle. Thus, less saturated and identifying types of inclusions on the sample of gems might sell more quickly than the more saturated unknown origin. That data set is compared to sets of (and expensive) ones. From the jeweler's point of view, data from reference gems of known origins, looking inventory turnover is very important and can result in much more profit over time. For this reason, some retail - ers prefer to use gems of lesser saturation in their designs to cater to this customer base. Gems that are so dark that it is difficult to see through Fig. 1-3. them are more difficult to sell and thus their cost usual - Illustration ly drops significantly. The optimal color can cause val - by Al Gilbertson, ues to significantly spike. In most cases (except bi-col - © GIA. ored gems), the color uniformity or evenness is also part of this value equation. Gems that face-up with multiple hues are usually less valuable than gems that show a sin - 2 u January/February 2016 Value Factors of Colored Gemstones The GemGuide for compelling evidence that indicates that the and topaz). Once gems get beyond a size that is common unknown is from a certain location. If the data over - for jewelry, the number of interested buyers decreases laps with gems from two locations or more, and GIA significantly, and the relative value per carat diminishes. cannot reach a definitive relationship to one location, However, note that exceptionally large gems from those the report has the result of “inconclusive.” locations with exceptional color (gems that aren’t too For collectors of crystals, “Herkimer” Diamond is a dark) are so exceptional that they can be very expensive generic name for a double-terminated quartz crystal dis - since they are rarely available from those locations covered in and around Herkimer County and the except as near-black gems. Mohawk River Valley in New York. In the high-end Subject to various issues with the rough material, the gem market, trade names have been used widely in the yield—the final carat weight of the gem compared to the jewelry industry to denote particular gemstone colors or initial weight of the rough—can be as high as 50% (very face-up appearances from specific geographic loca - rarely) or as low as a few percent; cutters evaluate the tions. The names were just as unlikely and profuse: various pros and cons when planning to cut the gem. “Paraíba” tourmaline, “Biwa” pearl, “Sandawana” Sometimes the best saturated colors only appear in larg - emerald, “Australian” sapphire, “Burma” and “Mogok” er sizes (e.g. kunzite or aquamarine), so that small ones ruby. Significant locations come and go. There is still of saturated color are rare and surprisingly expensive. strong consternation amongst many in the trade when a Conversely, if a deeply saturated rough is cut into a location is used as a name and the gem material isn’t larger gem, it can be too dark and not as valuable.

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