Diamond education. Learn about cut quality

To get maximum brilliance, fire, and ultimately "life" out of a diamond it must be cut to certain dimensions. Cutters must carefully consider each stone's optical properties to determine the optimum cut to give that diamond its "life". Each dimension is examined before qualifying for one of the five cut qualities:
(Ideal) - Very good - Good - Fair - Poor

TheDiamond.com only sells diamonds of Ideal, very good and good cut qualities.

The basic principles that show why a diamond’s cut is important can be derived from the
following diagrams. Optically, diamonds of all shapes behave the same.

Diamonds are composed of the following major parts:

In a well cut diamond (diagram 1A), most of the light entering the diamond from the top will bounce off the inner walls of the stone refracting back up through the crown, to give the viewer maximum brilliance and fire.

In diamonds which are cut either too shallow (diagram 1b) or too deep (diagram 1c), a substantial amount of light is lost through the bottom part of the diamond. This results in less light returning through the upper part of the stone to the viewer's eye - thus less beauty.

When evaluating cut quality, there are 3 physical features of the diamond that you must know. All 3 are in relation to the stone's diameter, in rounds, and in relation to the stones width for all other shapes.

1. Total depth percentage
This is the main factor in determining the life and brilliance of the diamond (shallow or deep stones will not look good - see diagrams above). The height of the stone is divided by the diameter in rounds or by the width in all other shapes. Ideal round diamonds should have a depth of 59%-62.5%. This is a relatively narrow range that has been proven to produce the best "brilliance" from the diamond. Brilliance is the light that is reflected back to the viewers eye. Flat and heavy cut diamonds will loose light through the bottom and sides of the diamond thus reflecting less light to the viewers eye. You can refer to our check list tables to see the range of depth percentages for all cut qualities. As we have mentioned only round diamonds have an "Ideal" range for depth%. Other shape's maximum depth% is "very good".

2. Table percentage (%)
The table is the big facet on the top part of the diamond. In rounds it is measured as follows: a/c x 100 = table %. Very big or very small tables will harm the stone's beauty. Only round diamonds have a standard for table size. Cut quality in all other shapes is more dependent on depth, girdle and length to width ratio.
In round diamonds for a diamond to be recognized as an "Ideal cut" the table must be relatively small. It must fall between 53% and 57%. Calculations have shown that tables in this range produce the greatest "fire" effect in the diamond. "Fire" is the reflection of light back to the viewers eye that produces the rainbow colors that are seen. Ideal diamonds have more of the "fire" effect than other cut diamonds. You can refer to our check list tables to see the range of tables for all cut qualities.

3. Girdle thickness
This is the part of the diamond that connects the bottom and top, and reveals the stone's quality of cut. The best girdle range for a diamond to fit in the "Ideal cut category for rounds" is anywhere between "Thin" and "Slightly Thick". This means that a girdle could be Thin, Medium, Slightly thick or any combination of the three, such as "medium to slightly thick". Extremely thick girdles are signs of bad cutting and should be bought cheaper. Extremely thin girdles may be prone to damage and should be avoided if possible. You can refer to our check list tables to see what a girdle has to be to fit into any cut quality range.

The possible girdle grades are as follows: Extremely thin, Very thin, Thin, Medium, Slightly thick, Thick, Very thick and Extremely thick. A girdle can have a constant girdle all around and could be "Medium" only or it could have a range (like most diamonds do) such as "Medium to Slightly thick". There are 34 possible girdle combinations.

POLISH AND SYMMETRY:

Polish is determined by the quality of finish given to the diamond. Tiny blemishes, scratches or surface graining can all lower a diamonds polish grade. All polish grades are determined with aid of x 10 magnification.

Symmetry is determined by examining the positioning and alignment of the diamonds facets. The better the alignment of the facets the higher the grade of the symmetry

TheDiamond.com will not sell diamonds that have any parameter or a final cut grade below a "good".

The possible cut grades we sell in a nutshell:

Ideal cuts (round diamonds only): Ideal diamonds are cut to maximize the brilliance and fire. Diamonds cut to these proportions reflect back all the light to the viewers eye.

Very good cuts: Very good cut quality diamonds are almost equal to Ideal cuts but may be slightly off in one category. They have slightly less brilliance and fire than an Ideal cut, but are cheaper.

Good cut diamonds: Good cut quality diamonds are the most common diamonds today. They will reflect most of the light that enters them and are very reasonably priced. Telling the difference between them and a very good cut diamond is hard.

A NOTE ABOUT OUR SUPER IDEAL DIAMONDS:

All our Super Ideal Diamonds are cut to the highest standard known to diamond cutters today. Only about 1% of all diamonds today fit these strict standards. The depth and table percentage of these diamonds are constrained to a very small range that maximizes the fire and brilliance of the diamond. A diamond will fit the Super Ideal range only if both it's polish and symmetry fall under the "very good", "excellent" or "ideal" (for AGS certification). Certification by the GIA and AGS - the 2 most highly recognized laboratories in the world.