This is a crucial and often overlooked factor in the evaluation of your diamond. We’ve been buying diamonds for over 40 years and can say without reservation that some labs are very strict in their Color and Clarity grades and some labs are soft in their grades.
When it comes to Cut, the numbers speak for themselves. However, Color and Clarity are subjective to a gemologist’s opinion. A single bump in either Color or Clarity grade will increase the market value of a 1 carat diamond by about 10% and a 2 carat diamond by about 20%.
If you view a diamond in our inventory that is priced substantially less than another diamond with similar Weight, Cut, Clarity and Color standards, take note of the lab that issued the grading report. The most reliable and strict grading reports are issued by AGS and GIA.
This does not mean that buying a diamond with a report from another lab is a bad deal. You should simply be aware that the Color or Clarity may be a grade lower than stated, and the prices are adjusted accordingly .
If you find what appears to be an extraordinary value on a stone evaluated by EGL, IGI, HRD, or AIG, we invite you to call our diamond buyer, Andy Marcum. He will evaluate the stone personally and issue an informal opinion. This is done at no cost to you and is probably more representative of the true value of the diamond you have in mind.
There are several articles in the trade press that document the differences in grade ratings from various labs. You can read more here, or ask any trusted local jeweler about their opinion. The industry consensus is broad and in general agreement about the reliability of grading from different gem labs.
Evaluating the Clarity Grade of a Diamond
The most important aspect to evaluating the Clarity grade of a diamond is to examine the “plot” or map of the stone. The plot is made by an independent gemologist looking at the diamond under a 10x magnification.
You need to be aware that not all certificates include a plot and be wary of those that do not provide one. When you read these plots, keep in mind that the flaws in a diamond rated SI2 or greater are “eye clean”; meaning that they cannot be seen with the naked eye.
Higher grades are more rare in nature and are more expensive. This results in you paying a premium price for quality that is not discernible without the aid of a loupe or microscope.
Here is a plot for an SI1 Clarity diamond that looks like it offers pretty good value. First, notice that most of the inclusions are toward the outer edge of the diamond. Inclusions toward the center of the diamond are more noticeable, and they reflect off other facets in the diamond.
Also, sometimes inclusions on the outer edge can be hidden under prongs when the stone is set, so they won’t be seen.
The top view of this plot indicates that there are several Needle inclusions near the outer edge, a small Cloud inclusion in the upper left area and a pinpoint Crystal inside the upper area of the table. However, none of these inclusions seriously degrade the beauty of this diamond.
The actual diamond images shown below illustrate the types of inclusions and how they will appear under 30X magnification in a diamond. These inclusions would not be visible to the naked eye.
Evaluating the Color Grade of a Diamond
Among all the qualities of a diamond, color is the most subjective, because it has no effect on the brilliance, fire or scintillation. You may be surprised to learn that diamond color is graded in loose stones by turning them upside down.
From the upside down angle, the nuances of color are very difficult to differentiate. Most people cannot tell the difference between a D and F color and this is true even for an expert grader.
When a diamond is mounted and viewed from the top down, it is even more difficult to see the difference between even a D to H Color. In terms of cost, each increasing grade will cost an additional 10% in a 1 carat diamond and about 20% in a 2 carat diamond. This is why we often advise customers who are looking for the best value to choose a G-H Color diamond.