The weight of a diamond is measured in carats, which is a small unit of measurement. Each carat is divided into 100 points. Therefore a 0.50 carat, or a half carat, may be referred to as a 50 point diamond. Carat weight is the easiest of the 4 C’s for gemologists to determine because of the use of sophisticated measuring equipment.
The measurements of a diamond are in direct correlation with its carat weight, if a stone is properly cut. Shallow or deep cut diamonds will not reflect the correct surface area the stone should have. The carat weight of a diamond has a large impact on the cost. The price per carat increases exponentially with the increase in weight. For example, the value of a 1 carat diamond will be greater than 2 half carat diamonds of equal quality.
Cut is the factor that fuels a diamond’s beauty and is considered to be the most important of the four C’s. Though extremely difficult to analyze, it is important to understand how a diamond achieves its brilliance, fire, and scintillation.
There is no single measurement of a diamond that defines its cut, but rather a collection of measurements and observations that determine the relationship between a diamond’s light performance, dimensions, and finish. There are many laboratories that determine the cut of a diamond. Israel Diamond Supply uses the top two laboratories in the jewelry industry, GIA and EGL. Each laboratory has its own terminology that is used when describing the cut grade of a diamond. GIA describes the cut using a range from Excellent to Poor, while EGL uses terms such as Ideal Plus, and Hearts and Arrows. This grading parameter has only been extended to Round Brilliant cut diamonds at this time. There is no industry standard for ideal or excellent cut diamonds other than Round Brilliant.
Polish and Symmetry are two important factors in the cutting process. Polish refers to the quality of a diamond’s surface, which can include nicks, abrasions, and polish lines. The symmetry grade refers to the alignment of the facets. Examples of poor or fair symmetry characteristics can include an off centered table, misshapen facets, or off center culet. On the GIA scale, the polish and symmetry are graded as follows: Excellent, Very Good, Good, Fair, and Poor. Israel Diamond Supply recommends choosing a diamond with a polish and symmetry grade of good, very good, or excellent.
Since diamonds are formed deep within the earth, under extreme heat and pressure, they often contain unique birthmarks, inclusions or blemishes. Inclusions are internal characteristics within a diamond whereas blemishes are characteristics related to the diamond’s surface. These characteristics can detract from a diamond’s brilliance and overall beauty. When a light vector enters a diamond, it is reflected off the facets and is returned to the eye as pure light. If there is anything disrupting the flow of light in a diamond, such as an inclusion, a portion of light reflected may be lost.
Diamond clarity refers to the absence of these inclusions and blemishes. Diamonds without these birthmarks are rare, and rarity affects a diamond’s value. Every diamond is unique. None are absolutely perfect under 10× magnification. Those that come close are known as flawless diamonds and are exceptionally rare.
The color of a diamond is a very important characteristic that affects both the look and value of a diamond. A diamond’s color is graded on the GIA scale from D-Z, with D being absolutely colorless and Z being light yellow. It is often very difficult to detect the difference between a colorless diamond and a near colorless diamond. Diamonds below the near colorless range will have a slight yellow tint that can be detected by the naked eye.
A light yellow diamond with proper proportions and minimal imperfections will still generate a nice brilliance.