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Today, the 4Cs of Diamond Quality is the universal method for examining the quality of any diamond, anywhere in the world.
The 4Cs includes: Carat, Color, Clarity and Cut. These four features directly reflect the quality and the value of the cut diamond.
The 4Cs of diamond hold different proportion in the value of each diamond as following indicated. Carat occupies 40%, color, clarity and cut respectively makes up 20% of the total diamond value. Therefore, the carat (weight) of a diamond is not the only index for diamond price. In order to determine the price for a diamond, all of these four features should be taken into consideration.

Carat

The Carat is the standard unit of weight for diamonds and other gemstones. One gram equals to 5 carats, and one carat can also be divided into 100 points. Diamond weights greater than one carat is expressed in carats and GIA calculate to the hundredth decimal place. Diamond dealer always use its ‘points’ alone to indicate the weight of a diamond below one carat.

diameter:5.15mm

diameter:6.49mm

diameter:7.43mm

diameter:8.18mm

diameter:8.81mm

diameter:9.36mm

diameter:9.85mm

diameter:10.31mm

diameter:10.71mm

diameter:11.10mm

Color

Color refers to a diamond chromaticity color. The main categories are colorless (white), near colorless and faint yellow or brown. The whiter or more colorless of a diamond directly affect its price and quality. Diamond color is a primary factor for determining its value. The following diamond color are categorized into sections, actually the diamond-grading scale is more precise. Therefore, from the consumers’ perspective, it is important to pay more attention on the certificate provided by some shops. The different of diamond color designations vary largely on the final price.

D-E-F: ColorlessThese three color-grades are the highest and rarest color grade. The differences in color between D, E and F diamonds can only be detected by a gemologist in side-by-side comparisons, and rarely by the untrained eye.

G-H-I: Near ColorlessThese three color-grades are most popular due to the fact that diamond with these color grades has more price advantages. When mounted diamond with these colors on gold jewelry, which would exquisitely cover the tiny hint of yellow color and better reveal the quality of the diamond.

J-K-L-M: Faint YellowDiamond with these color-grades presents noticeable faint yellow color. The faint yellow color is more visible when looking into the diamond from side-face instead of face-up.

Click to view examples of different diamond color grades.

Clarity

A blemish is a flaw found on the outside surface of a diamond. This type of flaw can be polished away with excellent diamond design, in order to enhance the quality of the diamond.

As diamonds form in extreme heat and under great pressure, small crystals can become trapped inside. This is a common inclusion, which affecting the clarity grade and value directly. The 5 standards, which are size, the color, the amount, the types, and the range of different kinds of visible inclusions, are measurements for diamond inclusion. In other word, these 5 standard inclusion measurements would directly reflected on the final price. Along with the development of technology, and the improvement of diamond processing, people are trying to minimize the presence and location of these inclusions. For instance, using laser drilling to fetch out the inclusions, or fracture filling to enhance transparency of diamond. A tiny laser beam is used to drill into the diamond, tunneling-in to remove inclusions. The signs of laser drilling are visible under side-view magnification. But after the diamond was exquisitely mounted on the jewelry, the signs of leaser drilling are almost invisible from face-up. The diamond’s clarity is a description of its internal purity when viewed from under 10x magnification glass. Clarity refers to two aspects, which are small imperfections internal the diamond (called inclusions) and on its external (called blemishes).

There are six diamond clarity grades:

Cut

A diamond’s cut is crucial to the stone’s final fire and brilliance. There are three attributes of diamond cut, fire (when light enters a diamond is split into all the different colors of rainbow), brilliance (the scattering of white light from the internal and external of a diamond) and scintillation (the reflected light in a diamond as it moves). When a poorly cut diamond with improper proportions looks dull and dark because it allows light to escape out the bottom and side. If it is cut too shallow, light leaks out of the bottom, too deep and it escapes out of the side.

The beauty of an extraordinary diamond is not only about its physical character and photonic features, but also reflects the cut from skillful diamond cutters. There are three aspects have to be taken into consideration when grading the cut, which are the quality of polish on facets, the symmetry of its facet arrangement and proportions.

Polish:Polish refers to the quality of a diamond’s surface condition as a result of the polishing process. While the polish categories reflect polish features on the surface. High quality of polishing will leave little to no scratches and marks, while a poor polish can result in imperfections on the surface of the diamond. The quality of diamond polishing process will eventually affect the brilliance.

Symmetry:Symmetry refers to how precisely the various facets of a diamond align and intersect. When the facets of a diamond are well balanced and aligned, the stone has symmetry, which is vital for creating optimal brilliance and scintillation. In diamonds with extremely deep pavilions, the whole surface of the table appears to be darker creating a ‘nail head’.

Proportion:Diamond proportion refers to the relationship between the size, shape, and angle of each facet of a diamond. There are five common metrics used to evaluate the proportions of a diamond, which are depth percentage, table percentage, crown height percentage, pavilion angle and girdle thickness.