The next four grades cover "nearly colorless" (G to J), which means diamonds with these grades will appear colorless when set in jewelry. The top three grades that indicate colorlessness for diamonds (D to F) vary subtly only by differences in transparency. (Note that this differs from the highest color grades for colored gemstones). The highest diamond color grade is colorless. Gemologists color grade diamonds on how close they come to colorless. The other factors (clarity, cut, and carat) will determine the gem's value. Unless a gem has an exceptionally pure green, red, or pink hue, color affects the value of all tourmalines equally. Tourmaline, for example, comes in every possible color. Color Grades for Moderate-Value Colored GemsĬolor has less of an effect on the gem grading and value of moderately priced gems. This 1.85-ct ruby has an "red-orange" color. To an expert grader, however, it makes a significant difference. For example, a slightly orangish ruby won't be worth nearly as much as a pure red. With high-value gems, subtle variations make a significant difference in gem grading and price. Warm colors, like red and orange, become shades of brown as their saturation decreases.įor colored gemstones, generally speaking, highest values go to stones with pure hues and strong, rich colors. Softer pastels may suit some people much better.Ī gem's saturation refers to the intensity of its hue. Bold colored gems aren't the best matches for every complexion or personality. Once again, however, consider what you want as a consumer. These will command special attention and pricing due to their rarity. As the grader continues going through the amethysts, only a few gems of the absolute deepest and richest coloring emerge. The same principle applies to the other grading factors, too. It wouldn't be the best gem choice for someone with a slight build. A small person couldn't wear such a huge stone gracefully. However, simply being larger doesn't make it better. Therefore, that feature will add to an amethyst's value. Since there are fewer large stones, they'll receive a higher grade in the size category than the smaller ones.įor amethysts, a 100-carat stone is rarer than a one-carat stone. This leaves the larger stones on top, demanding the most attention. The smaller stones will settle at the bottom of the pile. One of the first things the grader will notice is the size variation. Let's say, for example, someone just mined 100 pounds of amethyst and brought them to a gemologist for grading. Gemstone deposits will yield pieces with a wide variety of qualities. What's best for you may not necessarily be the "top" or rarest grade of the gem. When a gem receives a high grade for a property, that means it has rare features within that property. Ultimately, you'll purchase the gem that's best for you personally. Gem Grading and QualityĮven though we may use the term "quality" when describing the properties of gems, that doesn't necessarily mean that one gem is better than another. Round brilliant-cut spinel, mauve or earthy purple-pink, eye clean, 2.65 cts, Tanzania. However, first you must understand that gemstones are graded by the rarity of their features. I'll explain how we gemologists evaluate each of these properties and how consumers can use this information. Gemologists grade gemstones based on these properties. The "Four Cs" of gem grading stand for color, clarity, cut, and carat (weight).
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