At Colonial Jewelers, we follow the Gemological Institute of America (GIA)’s grading standards for Diamonds. In the 1940s, GIA created the 4 C’s, the universal standard for assessing Diamond quality: cut, color, clarity and carat. Together, the grading of each attribute contributes to determining the value of a Diamond, which is why all 4 C’s are important when picking out the perfect Diamond for you.
Sarah, the current President and Owner of Colonial Jewelers, and Jeff, her father and predecessor, are both GIA Graduate Gemologists, meaning they’re qualified to hand-select only the finest of Diamonds for our store. Our sales manager, Jill, is also a Graduate Gemologist and has helped to ensure our sales team is fully trained on the 4 C’s, as well as other extensive Diamond education, and are ready to share some of their knowledge with you and answer any questions that you may have.
The cut of the Diamond refers to the quality of the proportions and the symmetry of the Diamond. A Diamond’s proportions make a difference in how brightly your Diamond sparkles and shines.
On the GIA scale, Diamond cuts are graded from “Excellent” to “Poor” based on proportions that maximize light performance. An “excellent cut” Diamond returns nearly all the light that enters the gem, resulting in optimal sparkle and brilliance. A “poor cut” Diamond is the opposite in this way, with all of the light escaping through the bottom of the Diamond (the pavilion), giving the Diamond a dull appearance.
When a rough Diamond is mined, it is then evaluated to determine its best possible cut in order to maintain the maximum clarity, color and carat weight. The term “cut” is often confused with the Diamond “shape,” like round brilliant, or princess cut.
Fun fact: the other characteristics of a Diamond form during the growth process, but the cut of a Diamond is man-made: a result of the Diamond cutter’s skill and precision.
Diamond color actually refers to the absence of color, with completely colorless Diamonds being the most valuable and rare. The color of a Diamond is one of the most noticeable attributes, and becomes increasingly more noticeable as the carat weight increases. It also heavily impacts the price of the Diamond.
The GIA color grading scale ranges from colorless (D) to yellow or light brown (Z). Each letter grade signals a subtle increase in color saturation. Diamonds that fall beyond the scale’s range are considered “fancy colors” like blues, pinks and reds. Fancy colors are evaluated on a different scale.
The clarity of a Diamond measures the scale of how free a Diamond is from inclusions (internal) and blemishes (external). Diamonds are composed mostly of carbon, so inclusions are created during the heating process when other elements become trapped inside. Blemishes are created during the cutting and polishing process. Together, these elements create a Diamond's unique fingerprint.
Diamonds are viewed through a 10x magnification lens by Diamond graders. The GIA clarity scale ranged from “Flawless” to “Included.” Most Diamonds fall between the two ends of the scale, with inclusions that are so microscopic they don’t impact their beauty.
The carat of a diamond is a measurement unit describing the weight of the diamond. One carat equals 200 milligrams, which is roughly the weight of a paperclip.
While the 4Cs are each distinct in diamond grading, they still influence one another. For example, two diamonds with the same carat weight can appear different in size depending on shape and cut. A well-cut diamond maximizes surface area and light return, making it appear larger than a poorly cut diamond of the same weight.
Some people want the largest diamond possible. If size is a priority, we at Colonial Jewelers can help you find the best cut, color, and clarity for your budget and style. Many engagement rings can hold diamonds up to 5.00 carats, but each ring’s design and setting type affect size limits. Prong settings can be modified to fit nearly any diamond, while tension and bezel settings have more restrictions.
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From The Gemologist: How Colonial Jewelers Selects Diamonds 
Diamond Shapes 101
What You Should Know Before Shopping For A Diamond
Your Guide To Diamond Cuts
