4C’s Diamond Cut

Thursday, 1 July 2021
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Diamond Cut

 4C’s Diamond Cut

The diamond cut refers to the way the stone is fashioned and way the light is reflected and refracted through the stone. When cutting a rough stone the technician looks to maximise the size (carat weight) of the finished gem, which does not necessarily mean the finished stone has perfect proportions.

Why Is the Diamond Cut the most important of the 4Cs?

best cut diamond shapeOf all of the 4C’s the most important is the cut. Diamond cut can make or break the diamond as it relates to how well the diamond is cut and polished. It includes the depth and symmetry which effects how well-proportioned the stone is cut. A well-cut diamond reflects more white and coloured light back to your eyes which increases the sparkle whereas a poorly cut diamond looks dull and lifeless. The diamond cut has the biggest impact on the aesthetic look of the diamond and appearance.

Does Diamond Cut refer to the shape of the diamond?

No diamond cut does not relate to the shape of a diamond. There are many types of the shape of the stone, such as Emerald Cut, Oval, Square, Pear and a number of other shapes. The criteria that dictates the shape of a diamond is the size and shape of the original uncut stone. Some uncut shapes naturally lend themselves to a particular final cut to maximise the carat weight of the finished stone.

So What Does Cut Relate To?

The cut of a diamond refers to its reflective qualities (Brilliance and Fire), the proportions fo the stone, the symmetry of the facets and the scintillation . Each of these elements adds to the overall appearance of a diamond. The more precisely a diamond is cut the light it reflects and refracts and the more sparkle it has.

How Do You Know What The Ideal Cut Is?

GIA has a scale of grades relating to the Diamond Cut as detailed below:

Excellent – Excellent Cut Diamonds virtually all the light coming through the table of the diamond is reflected, and excellent cut diamond has the highest level of fire and brilliance and exceptional sparkle.

Very Good – A Very Good Cut Diamond also has a high level of brilliance and fire with the vast majority of light entering the diamond table being reflected. To the untrained eye very good cut diamonds are hard to distinguish from Excellent Cut diamonds.

Good – A Good Cut Diamond reflects less of the light entering through the table but still has brilliance and sparkle, but less fire. A good cut diamond is an option for a price conscious purchaser without having to sacrifice too much sparkle.

Fair – The proportions of Fair Cut Diamonds allow light to exit through the base and sides of the diamond so it exhibits very little brilliance. The best use for these stones are as side stones is a ring where they are not the feature stone.

Poor – A Poor Cut Diamond has very little sparkle, brilliance or fire as all the light passes though the stone and none is reflected.

Why Are Diamond Proportions Important

The three major proportions to consider are a diamond’s table, width and depth. There are recognised and universally measured standards that categorise a diamond’s cut, quality and excellence. These proportions are base on the ratios between the size, angle and shape of each of a diamond’s facets. It is generally accepted that a Round Brilliant diamond has 58 facets. This relationship affects the diamonds ability to reflect light and therefore the brilliance, fire and sparkle of the stone. Due to the shape of the rough diamond not all stones can be cut to maximise the reflected light without sacrificing too much of the diamond weight. The diamond cutters skill is to maximise the return on each stone which may result in a larger stone with less sparkle.

Diamond Cut Grade

What Do The Facets of A Diamond Do?

A round Brilliant diamond is optimises with 58 facets in total. Facets are small mirrors that reflect the light coming into the diamond back to your eyes. The placement, size and symmetry of the facets dictates the amount of light that the diamond reflects and refracts and the sparkle of the stone. There are facets both above and below the girdle and in the pavilion. If the facets are poorly proportioned or there are too few or too many the diamond will be less than ideal.

What Is The Diamond Table?

The diamond table is the largest facet, the large, flat surface which you see when you look at the diamond from above divided by the overall width of the diamond and expressed as a percentage. The table percentage depends on the shape of the diamond, and below we have listed the ideal percentage ranges for the more common diamond shapes.

Ideal Diamond Table Percentages

Diamond Cut TableAs you can see from the table above the ideal table percentage depends heavily on the Diamond Shape. If you have any questions about this complex issue please (phone and email) contact us and we will walk you through the options and factors.The above percentage sizes represent the table proportion that will optimise the brilliance etc. of the diamond. Once the table percentages move outside of these ranges, it can negatively affect the look of a diamond. A larger table size does not mean a better looking diamond, in this case bigger is not better. If the table percentage is too high, light doesn’t reflect off the crown angles and facets so there will be much less reflection of colour and the light will escape rather than being transmitted to the eye. Table percentage too low and the light becomes trapped inside the diamond and exits through other parts rather than to the eye. To get the best out of the diamond you choose stick closely to the above percentages and you’ll be rewarded with a classis appearance and masses of fire and brilliance from your diamond.

What is Diamond Width

A diamond’s width is determined by measuring from one end of its girdle (the diameter at its widest point) to the other end of the girdle. The width is most important when it comes to determining length to width ratio, which signifies how proportionate the diamond.

How Important is The Diamond Depth?

The depth of a diamond is measured as by the height of the diamond from the top of the table to bottom or culet. The depth is measured in millimetres and the depth percentage by dividing the depth by the width. The depth of the diamond is critical to its overall appearance. Too shallow or too deep and much of the light passes through leaving the stone listless and dull. The finest diamonds are cut within the optimal proportions to maiximise the light entering the diamond and the light reflected back.

Is there an Ideal Diamond Depth?

best diamond cut for sparkleIdeal Diamond Depth Percentages

There is no ideal depth as every diamond is different. The best depth consists of as ideal depth range depending on the cut of stone you choose. A diamond’s depth is given a grade, which can range from poor to excellent. Below, we’ve listed the ideal diamond depth ranges for all of the most common diamond shapes. Like with the ideal diamond table percentages we listed above, these ranges are intended as general guidelines only:


Basically a well cut diamond optimises the amount of light that strikes each facet. So instead of escaping through the diamond it is reflected back through the crown and the table. Excellent cut diamonds are generally more expensive than other cuts because they provide the best experience. When buyers are on a budget a smaller well cut diamond is preferably to a larger poorly cut one.

While ideal depth and table are important things to look for in a diamond it is important to remember they are not the only aspects of a diamond your should consider. The other three of the 4C’s,  color, clarity and carat, have an impact on look, feel and value of a diamond in different ways. As with Diamond Cut each of the other measures has a range of values which influence the price.

We would suggest that if you have any questions or are unsure if a diamond is right for you, please speak directly to one of our experts who can help you to understand exactly what you will get with every stone.

How Light reflects through a diamond


The brilliance of a diamond refers to the brightness of reflected white light. Look at the diamond face-up under a light and it should reflect a large amount of white light. If the diamond is cut too shallow or too deep or is not symmetrical then it will look dull and lifeless instead of brilliant.


The fire in a diamond is the amount of coloured light which is reflected off the facets and table of the diamond. Look at the diamond under a light or daylight and it should reflect a large amount of coloured light. If there is a a low level of coloured light reflected then the diamond is considered to have a low amount of fire.


Scintillation is the term used to describe the sparkle of the diamond as light moves on the diamond’s facets and table. The light sparkle as jt is reflected between light and dark areas on the diamond’s surface especially when the diamond is moving. This aspect of a diamond’s character is highly desirable and the higher the level of scintillation the more elegant the diamond. Low levels of scintillation can make diamonds appear dull.

Hearts and Arrows Cut Diamond

hearts & arrows diamondIf you are looking for a cut that will optimise the diamond cut then consider a ‘Hearts and Arrows” cut diamond. The original Hearts and Arrows cut diamonds were produced in Japan in the mid 1980’s. They were cut to the ideal proportions, and they were cut with excellent physical and optical symmetry. The diamonds were also cut to a very specific level of brilliance which results in the hearts and arrows pattern. Less than 1% of the world’s diamonds are produced with hearts and arrows optical symmetry. Cutting a diamond to this level of precision means more of the rough diamond is sacrificed and considerable additional polishing is needed to create diamonds with this precise optical symmetry. Production time can be three times longer to cut diamonds of this cut quality. Hearts and Arrows cut diamonds  are more expensive than average cut diamonds.


The terms Diamond Cut and Diamond Shape have distinct meanings. Diamond Cut refers to the process of optimising the diamond to reflect as much light as possible and working within the standardised parameters. Diamond Shape refers to the actual shape of the finished stone such as Brilliant Round, Pear, and Emerald shapes.

If you need expert advice on any aspect of diamonds and how the various 4C’s impact on cost and value please contact us on email showroom@anastasiasbroome.com.au or call us +61 8 9468 8116 at Anastasia’s of Broome.

Author Bio.

Jill Hansen runs Anastasia’s Of Broome and is a highly recognised expert is the field of South Sea Pearls having trained in seeding pearls in Cook Islands by Japanese Pearl Technicians. She established a wholesale pearl business selling pearls all over the world. Jill pioneered the combination of pearls and diamonds to create Lust™ Pearls, a unique fusion of these beautiful gemstones. She is an accredited diamond expert and is happy to use and impart her knowledge to help customers make informed decisions.


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