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Home >> Diamond Grading >> Diamond Shapes >> Diamond Cut

  The Cut Of A Diamond Is The Most Important Element Of Diamond Beauty.
  Select your favorite diamond shape below to learn important details about each diamond's cut quality. You can also scroll down or Click Here to read general information about Diamond Cut.


Popular Diamond Shapes and Cut Specifications.
Learn How Diamonds Are Cut.
The Sarin Diamond Proportion Analyzer.
Learn Why Most Diamonds Are Improperly Cut.
Learn To Identify The Common Heavy or Deep Cut Diamonds.
Understanding The Behavior Of Light In A Diamond.
Why GIA & AGS Have To Say About Cut.
Fancy Shape Diamond Guidelines (Ideal To Very Fine Cut)

Learn How Diamonds Are Cut: Diamond Cutters must choose between More Weight or More Brilliance.  When a diamond crystal comes from the ground, the brilliance, fire, and scintillation that constitute the unique beauty of a polished diamond are still locked within it. The way in which a diamond cutter decides to cut the new diamond ultimately determines the diamonds beauty and brilliance. The cut of a diamond is made up of many elements to determine the quality of a diamond's cut.  Gemological laboratories use sophisticated measuring devices to determine how well a diamond is cut.

The Sarin Porportion Analyzer is used by GIA and other gemological laboratories to analyze the following aspects of a diamond's proportions.

length, width & height
depth percentage
table percentage
girdle thickness
culet size
crown angle
crown height
pavilion angle
pavilion height
diamond symmetry.

Learn Why Most Diamonds Today Are Improperly Cut:

Many diamonds today are cut improperly. A flawless, colorless rough diamond crystal can be cut to very fine or ideal proportions to deliver the greatest balance of dispersion and brilliance, or it can be cut to inferior proportions which yield a diamond that displays very little brilliance but weighs slightly heavier.

Many people who buy diamonds today are unable to identify a diamond with inferior cut. Because diamond cutters have financial incentive not to remove weight from the rough diamond crystal, a great amount of diamonds sold on the market today have heavy or deep cut.

Learn To Identify the Common Heavy or Deep Cut Diamonds:

Diamonds are frequently cut for weight retention rather than to produce maximum brilliance. These “undersize diamonds” often weigh more than if they were cut correctly and can therefore can be sold for for a larger profit.

For example: an ideal or very fine cut one carat diamond measures 6.4 to 6.5 millimeters in diameter.  If you were to measure the diameters of most one carat diamonds on the market today, you would find many to measure between 5.9 and 6.3 millimeters.

These 1.00 carat, inferior cut “undersize diamonds” are no larger in diameter than ideal or fine cut diamonds which weigh 0.75 to 0.99 carats, and they exhibit significantly less brilliance.  We encourage you to choose a diamond that has ideal to very fine cut.

Understanding The Behavior Of Light In Diamond:

To understand diamond cut, it helps to understand how light reacts within a diamond. When light enters a diamond or any given material it bends or refracts.  The degree to which it bends is called the refractive index. The refractive index of diamond is 2.41, the highest of any natural transparent gem. In diamond the maximum angle of refraction is 24.5 degrees.  This is called the critical angle. Light traveling through a diamond is reflected if it strikes a surface outside the critical angle. Light striking a surface inside the critical angle will be refracted out of a diamond. The critical angle is represented as 24.5 degree cone in the diagram.

In a well-made diamond, a high percentage of light entering through the crown starts out striking the pavilion outside the critical angle. Thus it is totally reflected to the other side of the pavilion. There it strikes outside the critical angle again, and again and is totally reflected, this time towards the crown, where it strikes within the critical angle and leaves the diamond traveling in directions in which it can be seen. Such controlled release of light is planned leakage. If the pavilion is too deep, or too shallow, much of the light strikes inside the critical angle and leaks out the back of the stone rather than reflecting through the diamond and back through the top to the eye.
Learn What GIA & AGS Have To Say About Cut:

The Gemological Institute of America (GIA), and the American Gem Society (AGS), two highly respected gemological institutions, have developed different systems for evaluating diamond cut quality.  GIA has defined a range of proportion standards in which diamond cut quality is classified... Currently GIA's diploma study courses teaches GIA students seeking degrees in Gemology a system that assigns diamond cut grades in four separate cut classes: (See illustration below) Please note, GIA's Gem Trade Laboratory does not use the GIA cut class grade on its popular diamond quality report.
Guidelines For Ideal To Very Fine Cut In A Round Cut Diamond: (AGS 0 - 2)

The Information included below is based on information made available by Gemological Institute of America and the American Gem Society. These two institutions are the most honored in the world of gemological science.

This information below is a brief overview of diamond cut, and what you should look for in regards to diamonds of all shapes. Print this page and use it as a reference when choosing your diamond. You can refer to the diagrams to provide you with details that will help you select a round brilliant cut diamond that has ideal to very fine cut.

Read more about Ideal Cuts

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