In determining the quality of a diamond wedding ring, the cut carries the most weight (ironically, even more than the carat). In turn, many factors influence the quality of the cut, and many people find it difficult to judge cut quality because these factors do not always affect outward attractiveness. A diamond’s beauty goes beyond skin deep, however. When you’re looking for the highest quality diamond wedding ring for your money, pay the most attention to the diamond’s cut, following some of the guidelines here.
The way in which a gemologist cuts a diamond makes it look like a diamond. Diamonds in the ground look like plain, dirty stones, and you probably wouldn’t even recognize them as diamonds. To a gemologist, “cutting” a diamond doesn’t mean carving the jewel into a certain shape like a heart or hexagon, but it refers to shaving the back angle of the diamond so that light refracts in the most ideal way. The brilliance of a diamond wedding ring depends on how the physical properties and optical components of the diamond complement each other.
When cutting a diamond, a gemologist has to choose between more weight and more brilliance. Out of all the natural transparent gems, diamonds have the highest refractive index, which means that the diamond’s density affects light’s properties more than do other gems. Gemologists have calculated the critical cut angle that allows light to refract through the diamond most efficiently. When a gemologist cuts the jewel at an angle larger than the critical cut angle, the diamond will not lose as much in shavings, but it will not shine as brilliantly, either. Sometimes, gemologists will cut diamonds incorrectly so that they weigh more, but have less brilliance. You can recognize these “undersize” diamonds, as they are called, by asking for the proportion of weight to depth. For example, an ideally cut one-carat diamond should measure between 5.9 and 6.3 mm. If a one-carat diamond measures 6.4 or 6.5 mm, then the gemologist has cut it incorrectly.
When looking for a diamond, you should choose ones with an ideal or very fine cut, as opposed to a heavy or deep cut. A diamond with a very fine cut will appear white because when light travels into the stone, it hits the back at an ideal angle and returns back up and out. Since 1995, the American Gem Society (AGS) has developed a scale that rates perfectly cut diamonds as AGS 0, or the AGS ideal cut. Based on a diamond cutting design method founded in 1919 by the gemologist Marcel Tolkowsky, the AGS system has recently caught on with people looking for ideally cut diamonds.
A diamond with a heavy cut, on the other hand, appears darker because when light enters, it reflects to the back instead of up again. Gemologists rate lesser diamonds from AGS 1 to AGS 10, with AGS 1 being hardly distinguishable from AGS 0, and AGS 10 having noticeably inferior quality. In general, round diamonds have better AGS scores because it’s easier to cut round diamonds accurately than fancy shapes.
The AGS rating depends on three factors: the correct proportions of the diamond, the precise symmetry of the diamond, and the polish of the diamond. A jewel has to earn a 0 in each of these categories to receive an overall rating of AGS 0. Most AGS 0’s come in smaller sizes – less than 1.5 carats – because a gemologist has to spend a lot of time making exact cuts. AGS 0 diamonds usually cost about 10-15 percent more than others, too.
Watch out for deceptive advertising with labels that seem to ensure high quality but really don’t say anything specific about the diamond wedding ring’s characteristics. For example, a jeweler can call a diamond “ideal range” as long as it falls under a wide range of characteristics, but an “ideal cut” diamond has to have all the ideal qualities exactly. Also, just because a jeweler calls a diamond “Tolkowsky cut,” doesn’t mean the diamond follows the exact proportions based on light theories. When looking at diamonds, make sure you get the hard numbers: the table diameter, crown angle, pavilion depth, girdle thickness and cutlet size. But also remember that if a diamond catches your eye, then appearance always still makes the final decision in the end.
By Lisa Zyga