How to Grade an Emerald Cut Diamond

You can cut diamonds the same way you cut emeralds in order to give it a fashionable rectangular shape.

The Gemological Institute of America characterizes a set of grading standards for cut diamonds that are accepted all over the world. Diamonds are graded on the 4 "Cs": cut, color, clarity and carat weight. All gem laboratories grade diamonds on the same four characteristics despite different methods of scoring. An emerald cut diamond's grade affects the price of the diamond and is an indicator of overall quality. Although diamonds are cut into different shapes, the method for grading an emerald cut diamond, which features a rectangular shape with long, stepped cuts, is almost identical to grading the other diamond shapes as well.

Things You'll Need

• Light performance software
• Microscope
• Diamond gauge
• AGS Grading System Guide
• Loupe
• Electronic micro-balance

Instructions

1. Grade the cut of the emerald cut diamond. Measure the length, width and depth of the diamond using a diamond gauge. The diamond gauge determines these measurements in millimeters. An ideal ratio for the length and width measurements of an emerald cut diamond is between 1.5 and 1.75 to 1. Use the light performance software to determine how light travels through the diamond, and then analyze it with a microscope. The microscope allows you to examine the symmetry of the cuts of the emerald cut diamond. Perfectly symmetrical cuts indicate better light performance and in turn a higher grade. The GIA grades the cut on a 5-grade scale that includes grades of poor, fair, good, very good and excellent.

2. Grade the color of the emerald cut diamond. Professionally, color grades of individual diamonds are not official until enough color graders give the diamond the same color grade. Examine the diamond on a white background using a loupe or a jeweler's magnifying glass, and then compare it to previously-graded diamonds if possible. The GIA features a color scale that includes the letters D through Z. The D-end of the scale represents colorless diamonds while diamonds at the Z-end of the scale are categorized as light.

3. Grade the clarity of the emerald cut diamond. A diamond's clarity refers to imperfections in the diamond such as inclusions and blemishes or degree of flawlessness. Inclusions are internal imperfections while blemishes refer to external imperfections. Examine the diamond under 10x magnification and look for inclusions and blemishes. No diamond is perfect, which is one way to tell a real diamond from a fake. However, a diamond with a high grade of clarity will only have very minute blemishes. Clarity grades range from FL (flawless) to I1-I2-I3 (imperfect), with 11 different grades total.

4. Weigh the emerald cut diamond. A diamond's weight is measured in carats. One carat is made up of 100 points, with a carat equaling .2 grams or 200 milligrams. Place the diamond on the electronic microbalance, which will give you the diamond's weight in grams, and then convert the weight to carats.

References

• "Diamonds"; Marijan Dundek, 2009
• Gemological Institute of America: How GIA Grades Diamonds
• American Gem Society: AGS Grading System
• The Diamond Buying Guide: Emerald Cut Diamond Shape
• Jewel Basket: About Diamonds