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Jewelry and Colored Gemstone

Color is the most important determinant of value in color gems. It is also, too often, the principal determinant in erroneous identification because, unfortunately, most people don’t realize how many gems look alike in color. And even professionals in the trade can be misled or caught of-guard. Too often recognition and identification are based on color alone because so few jewelers and customers are aware of the large number of similarly colored stones that are available.

Until recently, the gemstone industry has promoted very few colored stones, concentrating instead on the more precious and profitable gems. But growing popularity of colored stones has expanded the market so that consumers now find they have a choice. If you want an emerald green stone but cannot afford a fine emerald, you might choose a green garnet (tsavorite), a green or “chrome” tourmaline, or perhaps green “tanzanite” (tanzanite is the blue variety of zoisite; now there is a green variety, which is sometimes called green tanzanite). And these are at least four gem materials from which to choose, no matter what color you prefer. New gems are being discovered each year, and known gems are being discovered in new colors. Increasingly, fine jewelers and designers are creating exciting pieces using the full color spectrum.

The four Cs of colored gems

We have already discussed the four Cs to consider in choosing a diamond, but colored gems have Four Cs of their own: color, color, color, and color! This statement may sound like an exaggeration, but not so much as you might think. Generally speaking, the finer and rarer the color, the less impact cutting, clarity, and carat weight have on the value of the gem. On the other hand, the more common the color, the more impact these other factors have.

When we discuss color, we are not talking simply about hue. Color science, and the evaluation of color, is a very complex area. But if you understand the various elements that must be factored into the evaluation of color, you can begin to look at colored gems in a totally different light.

Color is affected by many variables that make it difficult to evaluate precisely. Perhaps the most significant factor is light; the type of light and its intensity can affect color dramatically. In addition, color can be very subjective in terms of what is considered pleasing and desirable. Nonetheless, there has been extensive research and development in the field of color science, and experts are working to develop a viable color grading system. Gemologist at the GIA have produced a machine called Color Master, a type of visual color-meter, around which they have developed a color grading system that is gaining increasing acceptance. American Gemologist Laboratories has continued to develop its ColorScan system, and several other systems are gaining acceptance, one of the most promising newcomers being Howard Rubin’s GemDialodgue. Most gem pricing guides use at least one of these systems to describes the quality of the stones they are pricing, but problems still exist with color communication, and no solution seems imminent, and no system has yet replaced the ages old eye and brain combination, coupled with years of experience in the colored gemstone field.

The key elements in describing color

The color we see in gems is always some combination of pure spectral colors, which range from pure red to pure violet, coupled with varying degrees of brown, white, black, and gray. It is these later colors, in combination with spectral colors, that affect the tone of the color seen and that make the classification of color so difficult. For example, if white is present with red, you will have a lighter tone or shade of red; if black is present, a darker tone or shade. Depending upon the degree of gray, white, black, or brown an almost infinite number of color combinations can result.

As a general rule, the closer a stone’s color is to the pure spectral hue, the better the color is considered to be; the closer it comes to a pure hue, the rarer and more valuable. For example, if we are considering a green stone, the purer the green, the better the color. In other words, the closer it comes to being a pure spectral green, gemtv  having no undertone (tint) of any color such as blue or yellow, the better the color. There is no such thing in nature, however, as a perfectly pure color; color is always modified by an undertone of another hue. But these undertones can create very beautiful, unusual, distinctive colors that are often very desirable.

In describing color, it is often refer to these factors:

Hue: The precise spectral color (red, orange, yellow, green, blue, violet, indigo)

Intensity (or saturation): The brightness or vividness (or dullness or drabness) of the color

Tone: How much black, white, gray, or brown, is present (how light or dark the stone is)

Distribution: The even (or uneven) distribution of color
Both intensity and tone of color can be significantly affected by the proportioning of the cut. In other words, a good lapidary (stone cutter) working with a fine stone will be able to bring out its inherent, potential beauty to the fullest, increasing the gem’s desirability. A poor cutter may take the same rough material and create a stone that is not really pleasing, because the cut can significantly reduce the vividness and alter the depth of color, usually producing a stone is much too dark to be attractive, or one in which the color seems washed out or watery.

In general, stones that are either very light (pale) or very dark sell for less per carat. There seems to be a common belief that the darker the stone, the better. This is true to a point. A rich, deep color is desirable, but not a depth of color that approaches black. The average consumer must shop around and train the eye to distinguish between a nice depth of color and a stone that is too dark.

As a general rule, it is even more important to shop around when considering colored gemstones than it is when buying diamonds. You must develop an eye for all the variables of color; hue, intensity, tone, and distribution. Some stones simply exhibit a more intense, vivid color than other stones (all being equal), but only by extensive visual comparison can you develop your eye to perceive differences and make reliable judgment.
For example, let’s discuss the variations among rubies for a moment. The finest red rubies are Burmese. While they are not a pure red, these are the closest to pure. The tone may vary, however, from very light to very dark. As with most stones, the very light to very dark. As with most stones, the very light stones and very dark sell for less per carat. Burmese rubies are the most highly prized and the most expensive, because of desirability of their color and their scarcity. They also exhibit a beautiful red in all light, while rubies from other locations may exhibit a lovely red only in incandescent light ( such as you find in candlelight, lamplight, chandeliers, and most evening light) and become pinkish or purplish when seen in fluorescent light.

Thai rubies can vary tremendously in hue and tone, going from a light to a dark red varying degrees of a bluish undertone, giving them a purplish cast and making them look like the much cheaper reddish purple gemstone, the garnet. While some Thai rubies can have very fine color rivaling the Burmese (these are very expensive), most Thai stones are much less expensive than the Burmese, primarily because the color can’t compare.

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