HUES OF PARAÍBA TOURMALINE
As mentioned previously, the tone of Paraíba tourmaline is generally fixed at around level 4. Basic quality judgment starts with the beauty grade, followed by a consideration of hue. Although Paraíba tourmaline occurs in a very wide variety of hues ranging from green to violet, the special appeal of Paraíba material lies in its neon-like turquoise-blue or distinctive violet colors. The considerable difference in beauty between Paraíba green and common green tourmaline is difficult to see when viewed separately, but becomes apparent when the two are compared side by side. In the case of the turquoise-blue Paraíba material, the indisputable difference in beauty is easily appreciate even when viewed by itself. |
THE COLOR WHEEL
Hue refers to basic color, such as the reds, yellows, and blues seen in the rainbow, and the color wheel is circular arrangement of these hues. The Practical Color Coordinate System (PCCS) is constructed using 24 hues. The modified Munsell system uses an arrangement of 20 hues. Red, orange, yellow, green, blue, violet, purple, and their intermediate hues can be represented both numerically and by name. Paraíba tourmaline spans a wide range of hues from green to blue to violet. |
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JUDGING QUALITY
Start with an analysis of the beauty of the stone. By looking at the S, A, B, C and D grades to the next page, the approximate ranking from the very attractive S to the comparatively unattractive D can be understood. Different beauty grades of both the copper-green and turquoise-blue hues are included in the top and bottom rows. Within the same beauty grade, for example grade A, the blue stones are preferred by most people, resulting in greater scarcity and higher prices. (Incidentally, adjustment of the beauty grade to account for hue is also necessary in grading Thai rubies because they similarly occur in a wide range of shades.) In the case of Paraíba tourmaline, the key to understanding the beauty grade is to keep in mind that the turquoise-blue stones will command a premium price within a given grade.
As mentioned above, using the quality scale for Paraíba tourmalines begins with establishing the five levels of the beauty grade. Next consider any premiums associated with the different hues. Many people think that turquoise-blue is the most attractive color, and a premium price will reflect this.
Paraíba tourmaline also has its color made more attractive through heat treatment.
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