Independent and nonprofit, GIA is considered the final word on a diamond’s authenticity and quality. GIA developed the 4Cs and the International Diamond Grading System™, the grading standard adopted by jewelry professionals around the globe. GIA grades natural diamonds, screening every gemstone to identify synthetics, stimulants and known treatments. Expert gemologists examine each diamond under controlled lighting and viewing conditions, in order to provide the most rigorous assessments of a diamond’s 4Cs.
The value of a diamond is determined by its quality as defined by the 4 Cs: cut, color, clarity and carat-weight. Learn to recognize quality and value when choosing the diamond that's right for you.
Cut
The cut of a diamond--its roundness, its depth and width, the uniformity of its facets--all contribute to a diamond's beauty, brilliance, value and durability.
The width and depth have the greatest effect on how light travels within the diamond, and how light exits in the form of brilliance. The stone on the left is too shallow, and the one on the right is too deep. The center stone is a good cut.
Color
The term "color" is very important, but it is misleading--because the ideal diamond is characterized by a lack of color. The color tinting found in most diamonds is caused by minute impurities within the stone.The color of each diamond is determined by comparing it to authenticated "master" diamonds. Each stone is then color-graded to a precise scale from "D" (colorless) to "Z" (saturated).
Clarity
Virtually all diamonds have imperfections called inclusions and blemishes--scratches, trace minerals or other characteristics that can detract from the beauty of a diamond. Diamonds that are absolutely flawless are the most rare, and therefore, the most expensive.
Under the scrutiny of a jeweler's 10x magnifying loop or microscope, inclusions may be seen. These are nature's birthmarks; they may look like tiny crystals, clouds or feathers. The larger the inclusion, the lower the grade and the less rare the diamond.
The number, color, type, size and position of surface and internal flaws affect a diamond's value. Major inclusions can interfere with the path of light that travels through a diamond, diminishing its brilliance and therefore its value.
Diamonds are sold by the carat (ct), which is a unit of weight, not size. One carat weighs .20 grams. Since larger diamonds are more rare than smaller diamonds, the price increases in larger proportions as the diamond gets larger.
The term "points" refers to a diamond's carat weight. One point equals 1/100th of a carat. Therefore, a 1/2 carat diamond (.50ct) is referred to as 50 points.
What is Diamond Certification?
A diamond certificate is a printed report based on a gemological analysis of a specific stone. It is prepared in an independent laboratory by certified gemologists.
What Will a Diamond Certificate Tell You?
The certificate will state your diamond's 4 Cs: color, clarity, cut, carat weight. It will describe the diamond's shape, measurements, table and depth percentages, and grade the polish and symmetry. It should also comment on characteristics like fluorescence, graining, and imperfections.
Who issues a Diamond Certificate?
Diamond certificates are issued by independent gemological laboratories. There are several grading laboratories, the most prominent being: the Gemological Institute of America (GIA), the European Gemological Laboratories (EGL), the American Gem Society (AGS) and the International Gemological Institute (IGI).
