How Diamonds are Graded

When a jeweler or professional goes to buy a stone there are several things he will evaluate in order. Generally the stone is graded using the four C's of diamond grading. These are:

1. Clarity
2. Color
3. Cut
4. Carat

There are established methods and models for grading stones and one could reasonably expect to take a stone of a certain grade from one professional to another and come out with a similar rating. One should also remember this grading is subjective and there will be times when two accredited gemologists will give a different rating, possibly affecting the stone's value, by hundreds or thousands of dollars to the very same stone. It is wise to be able to at least make a good amateur estimate of the various rating points on your own instead of having to blindly depend on someone you may not know.

The first C is clarity. This is not the most important but is generally the first item looked at in a stone to be rated. Clarity does not refer to the concept of "being clear" with reference to a diamond. Clarity refers to the purity of the stone and lack of visible defects.

These defects or flaws or as they are properly known, inclusions, may manifest themselves as dark, black carbon spots, white carbon spots, small cracks, "clouds", feathers, or other areas of visible diffusion within a diamond or on the surface of the stone itself.

A truly flawless stone, one without any spots, cracks or inclusions, is very rare and extremely valuable. One can expect to find some flaws in most stones. The type of flaws, size of flaws, and location will have an effect upon the stone's value. It is important to learn how to judge a stone for clarity.

The Gemological Institute of America (GIA) has established a rating system for expressing the clarity of a particular stone. This rating system is based on the use of initials and numbers and goes on a one to 10 oriented system wherein 10 would be the best stone and 1 would be the worst stone.

This system is not expressed in simple numbers but with words and initials to further establish the rating scale. The scale is as follows:

• 10 - Flawless - no blemishes can be found.
• 9 - VVS-1 - no flaws inside the table. Possible very small internal flaws outside the table. If any external flaws are present, must be very minor.
• 8 - VVS-2 - very difficult to see flaws with 1 0x magnification power employed.
• 7 - VS -1 - flaws readily seen using 1 0x glass but almost impossible to see when the stone is viewed from from the back.
• 6 - VS - 2 - the back looking down through the stone.
• 5 - Sl - 1 - flaws unable to be seen with the naked eyes but quite apparent using 1 0x magnification.
• 4 - Sl - 2 - inclusion may include carbon spots or clouds or feathers underneath the table or larger flaws outside of the table.
• 3-1 - I- 1 to 3 - this is the least valuable group. They are heavily flawed and the flaws can be determined with the naked eye. There are going to be internal flaws inside the table, maybe clouds, groups of carbon spots, feathers and/or cracks that can be seen with the eye.

Legend:
VVS - Very, very, slightly imperfect
VS - Very slightly imperfect
Sl - Slightly imperfect
I - Imperfect

Source: Video Vindicator, 1992, BBS.