How to Evaluate Gem Stone Quality
Not all gemstones are created equal. Some sparkle brilliantly in the light, some have rich, deep colors, some are free of impurities and others impress us with their weight. According to the American Gem Society, all four of these properties figure into a gemstone's quality. These properties are often known as the four Cs--cut, color, clarity, and carat. The order of importance for the four Cs is different for diamonds and colored gemstones.
Admittedly, evaluating a gemstone's quality requires professional expertise, and opinions vary from jeweler to jeweler. Nonetheless, with the system developed by the American Gem Society, you can roughly evaluate the quality of your own gemstones.
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Instructions
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Instructions
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Evaluate the gemstone's cut. The American Gem Society's system accounts for proportions, symmetry and polish, but in general, the brighter a gemstone's sparkle, the higher its quality.
For a diamond, the effectiveness of the cut in bringing out the gem's beauty has the most weight in the overall evaluation. This is not true for colored gemstones, where color is the most important factor.
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Evaluate the color. Rich hues increase the quality of colored gemstones, such as emeralds, sapphires and rubies, for which color has the most weight in evaluation. For diamonds, the more colorless a stone is, the better.
Be sure to examine a gemstone's color against a white surface, as a colored background may hide undesirable hues.
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Evaluate the clarity. Under a binocular microscope, check the gemstone for blemishes and cracks, which diminish the quality. With diamonds, look for inclusions. Inclusions are small amounts of gas, liquid or other minerals trapped inside the diamond, and they lower its overall quality.
Generally, gems are magnified 10 times for examination.
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Weigh the stone to determine the number of carats. If your gemstones are unmounted, a sensitive scale can measure their weights. A carat is equal to one-fifth of a gram. For smaller gemstones, the measurements will be in fractions of a carat. If your scale is sensitive enough, you can find the weight in points. One point is equal to 1/100 of a carat.
If you don't have a scale, or if your gem is mounted in jewelry, dentritics.com can estimate its weight in carats (see Resource 2). Dentritics.com considers the type of gemstone as well as its cut and measurements. Gemstones that have the same dimensions may have different weights; for example, a diamond is heavier than any colored gemstone of the same size.
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Tips & Warnings
A jeweler's loupe or a strong magnifying glass can be used in place of a binocular microscope.
For accuracy, compare your evaluation with a certified jeweler's.
