Instructions

1

Remember that there are two international grading systems, named for the Gemological Institute of America (GIA) and the American Gemological Laboratories (AGL). With the GIA method, grading is done with the unaided eye using 10-power magnification. The AGL method simply uses the unaided eye.
2

Grade the color of the gemstone. The Colorstone Grading System is used to determine which of the 31 colors you should assign to the gem. You must also look for the jewel's tone (lightness or darkness) and saturation (color intensity) while appraising it.
3

Examine the gem for clarity. Inspect the stone for imperfections, such as cloudiness, cracks or inclusions (these can be a solid, liquid or gas trapped inside the gem). According to the GIA grading system, there are 8 levels of clarity.
4

Examine the cut of the stone. This determines how the light refracts off each surface, which affects the brilliance and beauty of the stone. If a gem is cut badly, it will be asymmetrical. This can ruin the reflective quality of the stone.
5

Weigh the gemstone to determine the carat weight. This measure gives the actual weight and mass of the stone, with one carat equaling 200 mg. Although carat weight is important, it is not the deciding factor in a stone's value. For example, a massive stone can be badly cut or contain impurities that may reduce its price considerably.