Symmetry & Polish

Symmetry & Polish

Symmetry:

Symmetry is the equality between corresponding parts of a stone. In rounds, the most common symmetry variations are

misaligned facets
facets failing to point properly
misshapen facets
off-center tables and culets
out of round girdle outlines
tables not parallel to girdle planes
wavy girdles (where the girdle plane resembles a warped record!)

Below are examples of these and other symmetry variations. On most diamond grading reports symmetry is either graded as

excellent
very good
good
fair
poor

When it comes to grading the cut of the diamond, another grading scale that is becoming more and more popular within the jewelry industry is the AGS (American Gem Society) cut scale. We will be discussing this even more when it comes to proportions, but AGS grades the symmetry based on a number scale going from 0 to 10. This is the scale that I use in my grading as the above descriptions are too general and are easily abused by many jewelers. Here is the grading scale as described by AGS.

0 - Extremely difficult to locate under 10x
1 - Very difficult to locate under 10x.
2 - Difficult to locate under 10x.
3 - Relatively easy to see under 10x, not visible to unaided eye.
4 - Easy to see under 10x, extremely difficult to to see with unaided eye.
5 - Very easy to see under 10x, very difficult to see with unaided eye.
6 - Obvious to see under 10x, difficult to see with unaided eye.
7 - Relatively easy to see with unaided eye.
8 - Easy to see with unaided eye.
9-10 - Obvious to see with unaided eye.

Usually, but not all the time, the symmetry characteristics of diamonds are pretty good and usually fall no lower than 2-4 or a "good" on the GIA scale. It is usually the older cut diamonds that fall lower than this.

Polish or Finish:

The execution of the design, the precision of the cutting details, and the quality of polish are collectively called "finish".

This is the icing on the cake. For maximum brilliance, sharp scintillation, and clear dispersion, good polish is essential. Diamond will take and keep the best polish of any gem, and good finish allows all of its qualities to shine and sparkle at their very best.

Many of the things that are considered under polish are really clarity characteristics: bearding, scratches, polish lines, nicks and pits. To these we add the condition of the girdle, facets and culet. Since these are very minor differences, the finish can only affect clarity grades such as FL, IF or VVS1. Symmetry and Polish are the only two kinds of cut grades that a GIA report gives you. When it comes to the more important aspect of proportions, you've got something to learn.