Use the four Cs system to grade blue topaz gemstones.
The most common grading system for all gemstones, including blue topaz, is the four Cs: carats, color, clarity and cut. While this system is often associated with diamonds, it is a useful tool for grading colored gemstones as well. When buying a blue topaz, you can assess some of the stone's characteristics on your own, but for a full and accurate report, you will need to take your stone to a professional gemological laboratory or to a gemological association.
Instructions
1. Weigh your blue topaz. The weight is measured in carats, as are all other gemstones, both precious and semi-precious. The ideal gemstone weight is at least one carat, as the unique properties of a stone will be better displayed at larger weights. Carats are also commonly expressed as a point system, with one carat equaling 100 points, thus making a .50 carat blue topaz equal to 50 points.
2. Assess the color of your stone. Professional gemologists look at hue, saturation and tone. Hue refers to the color, in this case, blue. Tone is how deep the color is in the stone; blue topaz, for instance, will have a light tone in comparison to stones such as sapphire. Saturation is the visual intensity of the color. All of these factors are relatively subjective, as people do not see color in exactly the same way. According to the American Gem Trade Association (AGTA), the most valuable stones are those that have a pure hue, medium tone and high saturation.
3. Look for clarity. Gemstones without internal flaws (inclusions) and external flaws (blemishes) are relatively rare, and are highly priced. However, many of these flaws are not necessarily visible to the naked eye, and because blue topazes are not as reflective as diamonds, the flaws may not affect the stone's brilliance.
4. Examine the cut of the gemstone. Look for key factors such as symmetry, polish and brilliance. These three factors will help the gem display to its best advantage. A wide range of cuts are available for blue topaz stones, but they will generally not be as faceted as a diamond, since blue topaz is not as reflective due to its coloring.
5. Obtain a lab report on treatments. Naturally occurring blue topaz is the rarest form of the stone; most natural topazes are colorless or shades of brown. However, heat and other treatments performed in laboratories can change colorless topaz into blue, making it the most common color available, according to the AGTA. Treatments and stone enhancements are often identifiable by reputable gemstone laboratories. A laboratory report can also tell you whether your stone is naturally occurring or created.
Tags: blue topaz, your stone, most common