Diamond Guide
Diamond 4Cs Standards
Diamond quality certification is based on the 4Cs, which widely uses the 4C standards, including the carat, weight, cut, clarity, and color of the diamond. The higher the 4C rating, the greater the value of the diamond.
Carat Weight
Carat weight is the standard measure of a diamond's weight, with 1 carat equal to 200 milligrams.
For diamond weight, 1 carat is equivalent to 100 "points," allowing carat weight to be precise to two decimal places. Jewelers can directly use “points” to describe a diamond weighing less than 1 carat, for example, a 0.25-carat diamond is also referred to as “twenty-five points.” For diamonds over 1 carat, they will be described in carats precise to the hundredth place, for example: a diamond weighing 1.08 carats will be described as “one point zero eight carats.
The larger the diamond, the rarer it is. Therefore, the price of diamonds tends to increase with carat weight. However, even if two diamonds weigh the same, their value (and price) can vary significantly. This is because the value of a diamond is determined by the other three standards in the 4C criteria: clarity, color, and cut.
The value of a diamond depends not only on its carat weight but also on the other 4C standards, all of which are essential.
Cutting
The high refractive index gives diamonds their brilliant sparkle, making them famous worldwide. Many people equate the cutting style of a diamond with its shape (round, emerald, square, pear, etc.). In fact, the grade of a diamond's cut is determined by the interaction of its facets with light.
To determine the cut grade of a standard round brilliant diamond, GIA calculates the proportions of each facet, which affect the diamond's appearance when viewed from the top. Thus, GIA can assess the brilliance of each diamond based on the interaction of light and facets:
Brightness: the white light reflected from inside and outside the diamond
Fire: the white light analyzed into a spectrum of colors
Sparkle: the scintillation produced by a diamond, as well as the patterns of light and dark areas caused by light reflection within the diamond
Additionally, GIA's cut grade assessment includes evaluating the relationship between the diamond's weight and diameter, the thickness of the girdle (which can affect the diamond's durability), the symmetry of the facets, and the quality of the polish of each facet, among other design and cutting techniques.
Clarity
Natural diamonds are formed from carbon elements subjected to high temperature and pressure, and this process also results in each diamond having internal characteristics, which we refer to as “inclusions,” while surface characteristics are called “blemishes.
The criteria for evaluating diamond clarity include the number, size, visibility, nature, location of the aforementioned characteristics, and their impact on the overall appearance of the diamond. Although there are no absolutely flawless natural diamonds, generally speaking, the higher the clarity, the higher the value of the diamond.
The inclusions and blemishes of diamonds are usually very small, visible only to professional diamond graders; to the naked eye, a VS1 diamond and an SI2 diamond may look identical, yet their quality and value can differ greatly. Therefore, professional and precise clarity grading is very important.
Color
For most precious diamonds, the color grading standard depends on its degree of colorlessness.
A chemically pure and structurally excellent diamond is colorless, resembling a pure drop of water, and has a high value. GIA established the D – Z color grading system, which determines the degree of colorlessness by comparing the diamond to different colored “master stones” under precisely controlled lighting and observation conditions.
GIA's D – Z color grading system is the industry-recognized standard for grading. D grade is the highest color grade for diamonds, representing completely colorless. From D to Z, as the color deepens, the diamond's grade gradually decreases; although the color differences between diamonds are very subtle and difficult for the average person to discern, they can lead to significant differences in diamond quality and price.
WILLS 5C – Evaluation
WILLS' criteria for selecting diamonds go beyond the 4Cs; diamonds are natural minerals that cannot be fully described in words. Our appraisers personally select the diamonds with the highest sparkle for clients, ensuring that the top quality is chosen based on the 4Cs, and provide a professional perspective to evaluate (Critic) the quality of the diamonds, informing clients of aspects worth considering beyond the certificate.
