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Diamond Cut And Cut Diamonds

Diamond cut – The most difficult of a diamond’s properties to understand let alone successfully evaluate whilst in the process of buying diamonds.

The cut of a diamond goes way beyond determining the outer shape, it influences the quality of a diamond’s symmetry, sparkle, brilliance and finish in relation to its proportions. This is called the “Make”.

To even begin to understand “diamond cut” a study of the most popular and easiest to illustrate loose diamonds – the “round brilliant” is necessary.

All other non round shaped diamonds are called “fancy shapes”.

  • What’s A Round brilliant Diamond?

  • How Does The Cut Relate To The Diamond?

  • How Are A Diamond’s Proportions measured?

  • How Do The Proportions Of A Diamond Relate To Cut Quality?

  • How Is The Make Described In Relation To Cut Quality?

  • What Other Factors Are Involved?

  • Squash It Down Into Bitesize Chunks.

What’s A Round Brilliant Diamond?

A round brilliant cut diamond is a brilliant cut diamond with 57 or 58 facets (flat angular surfaces) and a round shape. A brilliant cut diamond is simply a diamond cut in such a way (from the center out) as to optimize its brilliance.

The brilliance of a diamond is measured by the amount of light that is reflected back from the interior as well as top exterior of the gemstone.

Diamond Cut And Cut Diamonds

In other words it describes the intensity of light and brightness of a diamond.

How Does The Cut Relate To The Diamond?

When a bench jeweler cuts a diamond he/she can choose to make the most of a diamond’s brilliance and optical properties by spending time to optimize the cut or they can try to maximize a diamond’s carat weight by minimizing polishing and subsequent removal of some of the diamond.

This in turn varies the quality of the finished diamond. An optimized diamond cut will usually result in a slightly smaller and lighter stone with excellent brilliance and equal symmetry which will command a premium price.

A poor cut can result in the complete opposite but a diamond’s price can rise exponentially with weight. For example the price difference between a diamond just under a carat and one just over a carat can be huge. For the bench jeweler a poorer cut (added weight) will be worth it if the carat weight is borderline.

A diamond cut can be separated into three sections: top, middle and bottom or in diamond-speak: crown (top), girdle (middle), Pavilion (bottom).

The large flat facet that sits on top of the crown is called the table and is the largest of all the facets . On some diamonds there is fairly small culet facet present on the tip of the pavilion which helps protect a diamond from chipping.

N.B. All the facets are polished onto the face of the diamond using abrasion.

The girdle separates the crown from the pavilion and is the widest part of the diamond and it can vary greatly in thickness. The girdle can be faceted or left near rough depending on the quality of the diamond and the quality of workmanship involved in the polishing.

The relative proportions of table size, girdle width, pavilion height, crown height and overall height of the diamond will determine the quality of the cut. The quality of the overall polish will determine the quality of the finish.

These two factors together will determine the optical properties of a diamond.

It should be noted that a lot of antique diamonds are of a poorer cut quality than today’s diamonds so extra care should be taken when appraising these kind of stones.

How Are A Diamond’s Proportions Measured?

In 1919 Dr. Marcel Tolkowsky scientifically calculated the ideal proportions of a round diamond – this calculation came to be called “ideal cut” and some years later this calculation was slightly improved to produce the famous hearts and arrows cut.

The Tolkowsky calculation wasn’t perfect because it didn’t allow for varying thickness girdles and even some of the math calculation was flawed but the basic principles still more or less remain.

The relative proportions of table size (diameter), girdle width (diameter), pavilion height, crown height and overall height of the diamond are measured in millimeters and then the angles can be calculated.

These measurements can then be used to calculate the percentages of depth and table which in turn govern the optical properties of a cut diamond.

If the diameter is too wide and the diamond too shallow, light is lost through the sides of the diamond. If the pavilion is too deep light escapes from the bottom of the diamond. In either    case brilliance, fire and sparkle are diminished.

An ideal cut diamond will reflect light back from the diamond more efficiently than any other diamond which will maximize brilliance, fire and scintillation (sparkle).

N.B. Fire is the effect of light bending and splitting into it’s component colors through the prism of the diamond. Scintillation or sparkle can be seen when a diamond is tilted and moved a little i.e. when the jewelry wearer moves around.

How Do The Proportions Of A Diamond Relate To Cut Quality?

The individual measurements and the relevant depth and table percentages are shown on the diamond grading report that accompanies a reputable diamond and can be used in part to asses the quality of the cut.

This is not the be all and end all because the overall symmetry and finish of the diamond cut are also shown on the diamond grading report and thus a diamond cut or “make” can truly be appraised.

The make is not graded on the G.I.A (Gemological Institute of America) reports (these are the most common) so a table or chart of comparison is very handy. An individual jeweler uses a table/chart to judge and describe the cut/make to the customer.

How Is The Make Described In Relation To Cut Quality?

Hearts And Arrows: A hearts and arrows diamond will show perfect symmetry in round diamonds only.

The hearts and arrows is a variation on the ideal cut in that it’s optimized for brilliancy and symmetry and represents one of the best diamond cuts available.

Ideal Cut: As previously described an ideal cut is optimized for brilliancy no matter what carat weight is lost in the process. As with hearts and arrows the ideal diamond cut is only possible with round shaped diamonds that posses 57/8 facets.

Premium Cut: A premium cut diamond is almost as good as an ideal cut diamond as many people will find it very hard to tell the difference because these are fine diamonds by anybody’s standards. However, there is a slight difference and reduction in price over ideal cut diamonds.

Very Good Cut: Still in the realms of the finer diamonds, very good cuts stray slightly from the proportions of ideal cuts in order to maximize carat weight. These are less brilliant diamonds but still very desirable and offer the bargain hunter a good opportunity.

Good Cut: A good cut still reflects most of the light back but these cuts are generally created in order to save carat weight. Again some bargains can be found but some over priced specimens (borderline carat weight diamonds) fall into this category – buyer beware.

Fair Cut: Still reflecting good light, a fair cut is O.K. but again beware of diamonds of borderline carat weight (every quarter carat) as these are optimized purely for carat weight in this class.

Poor Cut: The diamonds that don’t make a good buy because they appear too dull and lifeless fall into this category.

The one thing to remember is that with the absence of a make grade on most diamond grading reports, it’s the jeweler who describes the cut and it’s the consumer who must verify the make from the proportions given in the diamond grading report.

What Other Factors Are Involved?

When talking about the make of a diamond every jeweler has his/her own terminology to describe the make. This can make things confusing so it would be wise to set the make as a numbered system (i.e. 1 to 5) in your own mind and then ask the jeweler to quote a number on the scale.

A diamond of average color and clarity will be enhanced by an ideal or very good cut whereas a diamond of excellent color and clarity will be spoiled by a fair or poor cut.

Polish and symmetry are still very important as they can affect the sparkle and overall finish of the diamond.

The diamond cut is widely regarded as the most important of the four C’s but don’t forget to appraise all four C’s before making your mind up.

Squash It Down Into Bitesize Chunks

  • The diamond cut goes way beyond determining the outer shape of a diamond.

  • Non round diamonds are called “fancy” shapes.

  • A brilliant cut diamond is a diamond cut in such a way as to optimize it’s brilliancy (reflected light).

  • An optimized diamond cut will result in a slightly smaller and lighter stone, a poor diamond cut will maximize carat weight.

  • A diamond can be separated into three distinct sections: Crown, girdle and pavilion.

  • A diamond’s facets (flat angular surfaces) are all polished onto the surface of the diamond using abrasion.

  • The relative proportions of a diamond describe the quality of a diamond cut and are listed on a diamond grading report.

  • Symmetry and polish describe the finish of the cut and are also listed on a diamond grading report.

  • In 1919 the ideal diamond cut was calculated using mathematical principles to calculate the optimum reflection of light back from a diamond. An ideal cut diamond reflects light more efficiently than any other cut – only round diamonds with 57/8 facets can achieve ideal cut.

  • Symmetry, polish and cut contribute to the make of a diamond. All jewelers have their own terminology for describing the make because most grading reports do not describe the make of a diamond.

  • A diamond of average color and clarity will be enhanced by an ideal or very good cut whereas a diamond of excellent color and clarity will be spoiled by a fair or poor cut.