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Diamond Grading

The jewelry industry uses several different standards for grading diamonds. The most commonly used and widely respected is the G.I.A. grading system. The G.I.A. system relies on four basic qualities. These are commonly referred to as the "Four C's". They are CLARITY, CUT, COLOR and CARAT WEIGHT.

The following is a guide to the G.I.A. Diamond Grading System:

1. CLARITY

F Flawless
I F Internally Flawless
V V S 1,
V V S 2
Very, Very small inclusions
V S 1,
V S 2
Very small inclusions
S I 1,
S I 2
Small inclusions
I 1,
I 2,
I 3
Included
  • Flawless (F) - IF the stone shows no inclusions and no blemishes under 10X power magnification viewed by a trained grader. These stones are rare and very uncommon even to those of us in the trade.

  • Internally Flawless (IF) - The stone shows no inclusions and only insignificant blemishes under 10X magnification. Normally what separates IF from F stones are characteristics that can be removed by minor re-polishing (light surface graining is an exception)

  • Very Very Slightly Included (VVS1 and VVS2) - VVS diamonds contain minute inclusions that are difficult for even a skilled grader to locate under 10x magnification. In VVS1, they are extremely difficult to see, visible only from the pavilion, or small and shallow enough to be removed by minor re-polishing. In VVS2, they are very difficult to see.

  • Very Slightly Included (VS1 and VS2) - VS stones contain minor inclusions ranging from difficult (VS1) to somewhat easy (VS2) for a trained grader to see under 10X magnification. Small included crystals, small feathers, and distinct clouds are typical.

  • Slightly Included (SI1 and SI2) - SI stones contain noticeable inclusions which are easy (SI1) or very easy (SI2)to see under 10X magnification. In some SIís, inclusions can be seen with the unaided eye.

  • Imperfect (I1,I2 and I3) - I-grade diamonds contain inclusions which are obvious to a trained grader under 10x magnification, can often be easily seen face-up with the unaided eye, seriously affect the stone's potential durability, or are so numerous they affect transparency and brilliance.

Just because two stones have the same clarity does not mean that they are of equal value.

Just remember that most of the above definitions apply when using a 10x power maginification device!! Which means that the stone looks better with just the naked eye!

2. COLOR

D, E, F Colorless
G, H, I, J Near Colorless
K, L, M Faint Yellow
N, O, P, Q Very Light Yellow
R - Z Light Yellow
Z+ Fancy Yellow


When I first started learning about diamonds, I was convinced that there was no point in buying anything less than a flawless stone. However, after becoming a little more knowledgeable (and practical), I quickly realized that the chances of my ever being able to own a flawless stone were pretty slim. In fact, to this day, I have yet to even see one!

What I suggest is that you first become informed about what the components of a diamond and itís grade. After that concentrate more on color than on clarity. A very large portion of the general public has little or no knowledge of diamond grading. But almost everyone knows when a diamond catches his or her eye. That is almost always due to color! Just because two Diamonds have the same color does not mean they are worth the same amount.

3. CUT

The cut of a diamond is very important; not only to be appealing to the eye but for proper light refraction. If a diamond is cut improperly it may hinder the color of the stone and the stoneís ability to refract light, therefore, making the stone less desirable. Here are a few of the most common diamond cuts:

  • Round brilliant
  • Marquise † (football shaped)
  • Emerald †(rectangular)
  • Princess †(square)
  • Oval
  • Pear †(tear drop)
  • Baguette †(tapered rectangle)
  • Trillion † (triangle)

Each shape or cut has an optimum size for each component of the cut as it relates to the other components.

Deciding cut is very simple. Basically all you need to do is select which cut appeals to you the most. Then try to buy one that is cut properly. By that, I mean that the proportions are within the guidelines and that the stone is appealing to your eye.

One small reminder. Letís say you were buying a round brilliant cut stone. Letís say the optimum girdle diameter for a 1 carat stone was 7.0 mm. You would not want to buy one that had a width of 6.2mm, but you might want to buy one that was 7.8mm. Why? Because the 6.2mm stone would appear smaller than it is and less appealing to the eye; therefore worth less. While the 7.8mm stone would appear larger than it is making it more appealing to the eye and worth more money! Just because two stones are of the same cut does not mean they are of the same value.

4. CARAT WEIGHT

This is another relatively simple component to understand. Carat Weight is the unit of measurement most commonly used in the industry to determine the exact size of a gemstone. There are 100 points to 1 carat. A carat is also equal to 1/5 of a gram (or there are 5 carats in 1 gram). Hence, a 1 carat diamond has 100 points, a ĺ carat has 75 points and a ľ carat diamond has 25 points. Diamonds are given a value based on four things. Just because they are the same size (weight) does not mean they are of equal value.

ADDITIONAL FACTORS

As you can see, the value of a Diamond is determined mainly by four things. The clarity of the diamond, the color of the diamond, the type of cut and of course, the size of the diamond. If one of these components lacks quality significantly more than another, then the value decreases dramatically.

There are additional factors that can affect the value of a Diamond. The type of certificate (or none) will affect the value of a Diamond. There are only 3 grading firms that are regarded as reputable in the trade.


I listed them in the most respected order. Just because a Diamond receives the identical grade from one or another firm, there is still a real market value difference.

  • Two identical Diamonds, one graded by GIA and one graded by EGL, the one graded by GIA will be worth 10-20% more.
  • Two identical Diamonds, one gradedd by EGL and one graded by IGI, the one graded by GIA will be worth 5-10% more.



Generally speaking, everyone regards the GIA as the most respected and accurate grading firm available today. None of these firms is not reputable, it is just the historical data shows that GIA is more consistent and less apt to be influenced by outside forces.

Flouresence is another factor that can greatly affect a Diamonds value. This particular attribute can seriously detract from a Diamonds ability to reflect light. In essense, if the Diamond has high flouresence, the light entering the Diamond is "soaked up" or diffused by the Diamonds flouresence. So, a Diamond with some or more flourescence is worth less or significantly less than a Diamond with the same grade, shape, weight and certificate and no flouresence.

Again, letting your instinct guide you is the best course of action in the beginning. Asking a jeweler to allow you to compare Diamonds side by side is always a good way to judge "how good the deal is". But basically, if you like it and it sparkles in your eyes, then you should be happy-ever-after.