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Gemstone Grading

by Lexi, Customer Advocate, Research and Resource Development Group,
Exclusively for Fire Mountain Gems and Beads®

There are a lot of steps to grade a gemstone. Each step of grading focuses on a different feature and has many details that create the overall grade determination. It can be difficult to understand gemstone grades without training, so with the help of the Fire Mountain Gems and Beads gemologists we've created a chart to help clarify the basics. Images of both emerald and lapis lazuli are shown to illustrate transparent and opaque versions of each grade. There are other factors taken into consideration when grading colored gemstones such as the quality and rarity of the material, enhancements, overall size of the stone, uniformity of shape, quality of cutting/faceting and the combination of graded features.

Grade Hue and Color Saturation Color Tone Inclusions Transparency/Opacity Cutting, Surface, Drilling
Color is the hue expected. Color saturation is vivid and even througout the stone. Color tone is rich, but not so dark as to be near the far end of the spectrum. There are few, if any, inclusions. Any inclusions will be small and hard to spot with the naked eye. Translucency/Opacity is as expected for the specific stone. Cutting or shape is uniform. Surface has a smooth luster, high polish and no cracks or chips. The drilling of the hole is even and uniform.
Color is the hue expected, but may not be as vivid as an A grade. Saturation is fairly even throughout the stone. Color tone is good, but may be lighter or darker than an A grade stone. A few inclusions are seen, but they are small and unobtrusive. The stone may not have the clarity or opacity of the same stone in an A grade. Cutting or shape may exhibit some slight variances. Surface has a medium luster and moderate polish, cracks or chips are minimal and drilling is generally uniform.
The color of the stone is within the hue expected, but may not be vivid or even. Color tone is significantly lighter or darker--near the ends of the spectrum. Inclusions or matrix mineral content is more apparent and frequent. These will be easily visible to the naked eye. The stone may vary greatly in clarity/opacity from that expected. Cutting or shape exhibits some variances. Surface has a medium to low luster and polish. Cracks or chips are more apparent. Drilling may lack uniformity.
Color of the stone is generally the color expected, but saturation is low and very uneven. Color tone can be so deep it seems black or so light it seems colorless. Inclusions are frequent and greatly affect the overall look of the stone. Stones expected to be transparent may be opaque or be heavily included. Stones expected to be opaque may have less original material and more "other" mineral content, causing more transparency. Cutting or shape can be irregular. Surface has poor luster with cracks or chips. Drilling can be uneven.

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