Diamond Education: Cut

What makes diamonds stand out beyond any other precious gemstone is their fire and brilliance. While nature determines the color and clarity of a stone, diamond cut is dependent solely upon the skill of the cutter.

The cut of a diamond is what determines how the light that enters the diamond is reflected and therefore how much fire and brilliance the diamond will exude. A diamond that is cut too shallow with respect to its width will allow too much light to pass straight through the diamond, leaving little light to reflect. Such a diamond will appear dull and lacking in brilliance. Conversely, a diamond cut too deeply will allow light to escape from the sides of the diamond, also appearing dull.

Mouse over to see the effect of the diamond cut.

The depth and table measurements, which are used to determine how good the cut is, are given in percentages of the girdle (the widest part of the diamond). So, if a diamond's girdle measures 10 millimeters, the table measures 5.6 mm, and the total depth measurement is 6.25 mm, it would have a table of 56% and a depth of 62.5%. What percentages will yield an ideal cut vary from shape to shape. The table below gives percentage ranges of a good cut for different shaped diamonds.

Shallow Cut:

Light is lost out the sides, causing the diamond to lose fire and brilliance.

Deep Cut:

Light goes straight through the diamond, causing it to appear dark and dull.

Ideal cut:

This is a very rare cut, that reflects nearly all light that enters the diamond and creates the maximum fire and brilliance.

Premium cut:

Reflects almost as much light as the Ideal Cut, but for a lower price, and is a Yadav recommended buy.

Good cut:

Reflects most light that enters the diamond, but not as must as a Premium Cut diamond. This is less expensive than the Premium Cut and is a Yadav recommended buy.

Fair cut:

These still are a quality diamond, but a Fair Cut diamonds will not be as brilliant as a good cut.

Poor cut:

All the diamonds that do not meet the Fair Cut quality standards are placed in. These diamonds are deep and narrow or shallow and wide and tend to lose most of the light out the sides and bottom. Yadav does not carry Poor Cut diamonds.

Depth & Table Measurements

Loose Diamond Table   Loose Diamond Depth

  Depth Table
Round 60 - 62.9% 54 - 58%
Oval 58 - 66% 54 - 63%
Emerald 60 - 66% 60 - 65%
Marquise 58 - 65% 54 - 60%
Pear 58 - 65% 54 - 60%
Heart 54 - 59% 55 - 60%
Princess 68 - 75% 65 - 75%
Radiant 68 - 73% 65 - 75%

In order to cut a stone to ideal proportions, much of the rough diamond is sacrificed, leaving a stone with a smaller carat weight. Diamond cutters sometimes sacrifice ideal proportions to end up with a larger, more profitable stone. Industry standard valuation of diamonds (Rapaport) does not take into account a diamond's proportions, thus a larger stone with fair proportions will be worth more than the smaller one with good proportions to a diamond cutter (color and clarity being equal). Consequently, ideal cut stones are very rare and hard for wholesalers and retailers to find, and as the consumer, you will see that retail jewelry stores price accordingly.