How to Grade Set Gemstones


Step 4: Gem Grading

Lesson 4

Assessing each of the Four Cs (Carat, Cut, Clarity, and Color) for a set stone presents challenges. We’ll go through each of these categories and also consider the differences between grading mounted colored gems and diamonds.

Carat Grading Set Gemstones

Removing a gem from its setting for weighing is possible but rarely done. The primary exception is when there’s a serious discrepancy between your weight estimate and what the customer or supplier says a stone should weigh. Removing a stone requires a competent bench jeweler and, thus, additional time and expense. You’ll also face the risk of damage to the stone or setting. If necessary, for high-value stones, jewelers will usually cut the prongs rather than pry out the gem. Of course, they must then re-prong the setting.

Weight

You can calculate a gem’s weight by its proportions. You can usually measure the dimensions of a set stone directly. Where this isn’t possible, you can estimate a measurement. Take as many measurements as you can and estimate the rest. The accuracy of your estimate is determined by the quality of your instruments and how carefully you use them. You need …

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Full Article Details


Content Length 2239 words
Reading time 11 min 12 sec

Here's what you get if you unlock this article:

  • Carat Grading Set Gemstones
    • Weight
    • Depth
    • Diameter
    • Melee
    • Melee Weight Chart
    • Baguette-Cut Gems
    • Converting Measurements to Weight Estimates for Set Gemstones
  • Cut Grading Set Gemstones
    • Table Size
    • Crown Angle
    • Girdle Thickness
    • Pavilion Depth
    • Culet Size
    • Completing Your Cut Grading
  • Clarity Grading Set Gemstones
    • Assigning a Range of Clarity Grades
  • Color Grading Set Gemstones
    • Color Grading Diamonds
    • Color Grading Colored Stones
      • How Settings Affect Colored Gem Tone
      • Effects of Metal on Colored Gemstones
  • Reporting Grades for Set Gemstones

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