How to Figure the Carat Weight
Jewelers define the term carat in two different ways. As it pertains to gold, silver and platinum, carat means the purity of an alloy. In the carat purity scale, 24 is the highest level and 1 is the lowest. The purity of better gold is stamped somewhere on the piece of jewelry.
When jewelers refer the carat of a gem or stone, they mean its weight. In gemology, a carat is a unit of weight equal to 0.2 grams, or 200 milligrams. You can find the carat weight of a gemstone using a finely calibrated digital scale. Knowing the carat weight is useful if you want to appraise or sell your jewelry.
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Instructions
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Place your loose gem in the center of the scale's measuring pan. Depending on the device, it may weigh the gem automatically once you set it on the scale, or you may need to press a button to initialize the weighing process. Read your device's documentation.
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Record the weight of the gem in milligrams as it is displayed on the scale's screen. For example, the weight a small diamond taken from an engagement ring may be 30 mg.
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Divide the milligram weight by 200 to obtain the carat weight. For example, a diamond that weighs 30 mg weighs 0.15 carats, since 30/200 = 0.15. A jeweler or gemologist calls this a 0.15 ct. diamond.
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Tips & Warnings
In gemstones, other characteristics help give the stone value besides carat weight. Color and clarity also help determine the quality of the gem.
Higher purity gold and silver is softer, so depending on the use for jewelry, a less pure, but harder metal may wear better over time.
References
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