A diamond’s grade is often what determines its price and value. Most diamonds sold in jewelry stores and online stores come with a diamond grading report that illustrates its qualities and specifications. Larger, higher-grade diamonds typically come with a grading report from a reputable third party institute like the Gemological Institute of America (GIA), EGL, AGS, and others.
A diamond’s grade is determined by the 4Cs (cut, color, clarity, and carat weight). While there are other factors that can affect a diamond’s physical appearance and value, the four Cs of a diamond are the most important characteristics. As such, gemologists worldwide use these four parameters to determine the grade of most diamonds.
Diamond Grade Chart
When buying a diamond, one of the most important factors you should consider is its cut grade. The cut determines a diamond’s physical appearance and as such, should be prioritized. Diamond cut is graded from excellent (provides maximized brilliance, reflects the most light back to the surface) to poor (most light escapes at the bottom or the sides of the diamond, providing little to no brilliance). Below are the most important parameters that determine a diamond’s cut grade:
A diamond’s cut proportions affect the stone’s fire, brilliance, and scintillation. It is determined by how each facet in the diamond is angled, sized, and shaped. In a well-cut diamond, each facet is strategically placed so that the most amount of life is reflected out of the crown for the observer to enjoy. A poorly cut diamond (i.e. too shallow or too deep) does not reflect much light because the facets allow the light to escape from the bottom or the sides instead of being reflected back to the observer’s eye.
As the term suggests, symmetry refers to how symmetrical the facets of each diamond are in relation to each other (i.e. how each facet aligns and intersects). A diamond’s symmetry is graded from excellent to poor.
Polish is determined by how smooth the facets are in a diamond. A diamond with an excellent polish will not show any defects even under 10x magnification whereas a diamond with poor polish will show defects even without magnification.
Other factors that determine a diamond’s cut grade include girdle width and culet size, which also affect a diamond’s brilliance and overall appearance.
In colorless diamonds, color grade refers to the amount or lack of color in a diamond. The more colorless a diamond, the higher its color grade. Colorless diamonds are more valuable than diamonds that show a yellow tinge.
Colorless diamonds in the D, E, and F color range are the most expensive of all. Diamonds in the G to J range are still near colorless but there is about a 10% price difference in each color grade. Diamonds in the I and J color range have the most demand in the market because they are readily available and offer great value for money.
All diamonds contain inclusions (defects or blemishes within the diamond). Inclusions can affect a diamond’s physical appearance, as it can interfere with the passage of light in the diamond, which in turn can affect the amount of light reflected back to the surface. A diamond’s clarity grade determines the amount of inclusions in the diamond. When grading a diamond, gemologists consider several factors including the position, size, and quantity of these inclusions under 10x magnification. Inclusions that are located in the girdle or under the bezel of a diamond is ideal because they are not visible and barely affects a diamond’s brilliance.
The GIA uses 11 categories for a diamond’s clarity these include: flawless (FL), internally flawless(IF), very very slightly included (VVS1, VVS2), Very Slightly Included (VS1, VS2), Slightly Included (SI1, SI2), and Included (I1, I2, I3).
Brilliant cuts are more forgiving of inclusions because their facets are positioned in such a way as to maximize brilliance whereas other fancy cuts like the emerald cut and asscher cut (which are step cuts) are less forgiving of inclusions.
Of all the qualities of a diamond, the carat weight is probably one of the most important for most people. Diamonds can significantly increase in price and value the bigger it is. This is because rough stones that can produce a 1-carat diamond is rare. This is why price increases so much as you go up per carat.
It is worth noting, however, that carat refers to a diamond’s weight and not necessarily its size. The size of a diamond is determined by its diameter and crown size. This means that two diamonds of the same carat weight may not necessarily have the same physical size when viewed from the top. Its cut proportions determine the actual size of the diamond; carat weight merely refers to how heavy the diamond is. The length x width ratio of a diamond also determines how big it will appear once set in a ring.
All the characteristics mentioned above determine how valuable a diamond is and are therefore, dependent of each other. While no two diamonds are virtually the same, these parameters help jewelers and consumers determine the price and value of a diamond.