Cut is one of the four imperative criterions that you need to consider while purchasing a Diamond. The Cut of the Diamond is mostly influenced by man; a touch of dexterity that exposes the Diamond’s hidden splendor. However, don’t confuse ‘Cut’ with ‘Shape’ of the Diamond. Definitely, it is the meticulous precision of different cuts that gives a Diamond its shape. In gemological terminology, Cut refers to the geometric proportions of the Diamond. Cut is a symmetrical arrangement of facets that enhance the appearance and shape of the stone. These geometric aspects play an important role in defining the character of a Diamond.
Cuttings results in the display of brilliance that’s the result of three steps-
Refraction of Light
Dispersion of light
Luster- The shinning of the reflected light
A Diamond sparkles when the light is refracted from the crystal. This is a combined result of both external luster and internal reflection. The external reflection is enhanced through polishing, while the internal reflection is improved with the cut.
The whole theory of Cut works on two primary factors refraction and dispersion. Diamond cutters have to consider the Refractive Index (RI) and the Dispersive power. RI- the amount of incident light reflected back- is responsible for the brilliance of the diamond. Dispersive power is the ability of the diamond to split the white light into its spectral color called fire. While designing the cut the craftsmen need to cut the diamond creating interfacial angles for maximum refraction. The goal is to attain total internal reflection, the more exact the proportions more brilliance/fire it will display. However, shape and size of the crystal also influence the cut.
The Diamond cutter has to meticulously maintain the symmetry of the facets while cutting the crystal. A cut is formulated using the proper mathematical symmetry, it is the alignment of the facets. If the alignment is not proper, the diamond will not refract the maximum light. The diamond symmetry too can be graded as Poor, Fair, Good, Very Good, or Excellent.
The light travels differently in various diamond cuts and you can see how in the following pictures.
Maximum light in this cut that enters through the crown travels across and is refracted back result- best brilliance. Shallow Cut Diamond
In the shallow cut diamond, much light leaves from the pavilion, it cannot travel down for refraction, making the diamond appear worn out. Heavy or Deep Cut Diamond
In deep cut diamond most of the light entering the diamond leaks out through the sides after refraction. This results in poor brilliance and Diamond too appears very dark.
A poorly cut diamond allows the light to escape while a well cut i.e. good cut create multiple mirrors with its proportional facets. This creates amazing brilliance in the diamonds that dazzles our eyes.
In Ideal cut diamond light travels through the table travels to the pavilion, where it is reflected from one side to another escalating in the facets before reflecting back to your eye.
The latest technology allows us to measure the cut of the diamond with the Dimension system. This computerized system accurately measures the diamond proportions.
To understand how cutting achieves the desired result let us understand the anatomy of the Diamond Cut.
The above cut aspects are better known in the gemological terminology as facets. The facets radiate outwards hence they are positioned that the light coming through them interplays to enhance the diamond’s brilliance.
Effect on the overall character of diamond
The upper facet of the diamond ascending from the girdle to the flat table
Balance, Brilliance, Dispersion, and Scintillation
The broadest diameter encircling the edge of the diamond.
Provide the body to diamond for the setting it in the jewelry prongs
The facet narrowing down from the girdle to the tip of the diamond
Reflects light back up through and through the crown of the diamond.
The pointed tip at the bottom of the diamond.
Forestall Chipping at the tip. Emerald Cut Diamond does not have a culet.
Is a flat facet at the top/crown of the diamond
Refracts maximum light from the lustrous surface.
Distance measured between two opposing points along the girdle's outline.
Helps to determine the cut grade
Is measured as the total length downwards from the table flat to the culet.
Helps to determine the cut grade
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Types of Facets in a Brilliant Cut Round Diamond
The flat top most facet of the diamond and the most important facet, it will usually influence the brilliance and fire of the stone. Star Facet
Beneath the octagon table on the round brilliant cut are eight facets known as the star facets. Kite or Bezel Facets
These facets look like a four-sided kite and expand from the table to the girdle of the round brilliant diamond Upper Girdle Facets
These triangular facets adjoin the kite facets on top and border the upper girdle of the Diamond. Pavilion Facets
These facets are on the underside of the diamond joining the lower girdle facets, shaping down to the culet. Lower Girdle Facets
These elongated triangular facets border the lower girdle narrowing down the diamond.
These are the basic facets, modified to create different shapes. The following chart gives the number of facets in every cut. Diamond and its Facets
The grading of the diamond cut is very crucial to determine its value. The Gemological Institute of America (GIA), the paramount diamond grading authority has stringent methods of diamond cut grading. They divide the diamond aspects into two aspects related to appearance and craftsmanship. Brightness, Fire and Scintillation are appearance-based where as the Weight Ratio, Durability, Polish, and Symmetry are the result of the design and craftsmanship. GIA calculates the cut grade based on the different facets angles, table, girdle, diameter measurement etc. The cuts are graded as
However the cut quality can be derived by grading the two key factors that affect its quality- table percentage and depth percentage. The grading reports of the diamond exhibit these parameters in percentages by using the formulas below
For a round brilliant cut diamond, table percentage is accounted as follows:
Table (%) = longest table measurement (in mm)
average girdle diameter (in mm)
While for depth percentage:
Depth (%) = depth (in mm)
average girdle diameter (in mm)
The following chart is the example of the proportion criterion that will determine how much light your diamond will reflect back to the eyes.
Here are a few Proportions Criteria shown for the three popular cuts
It was in the middle of 14th century, the diamond faceting received a facelift with the introduction of the polishing wheel. The facets became more detailed and comprehensive the diamonds too began to appear brighter than their former counterparts. In the same period rose cut was introduced which made diamonds………
Initially, until the augment of 11th century diamonds were used in their uncut forms for jewelry. A theory developed that diamond appearance could be augmented using grinding and polishing. Diamond dust was used to polish the diamond angles to form a pointed tip and a smooth unblemished appealing design. Point cuts appeared on the diamonds from the Middle Ages until the Renaissance era.
Among the various cuts that began to surface in the history of gemology, table cut was the first major faceted diamond cut. The point cut was modified, cutting the point to get a flat facet, better known as the table. However, the fire and dispersion was still over looked even with the improved old single cut. It was just a sparkling hard stone, ruby and emeralds being more valuable.
Table cut was further modified to suit the contemporary jewelry requirement and to enhance the diamond look. In order to improve the brilliance of the stone eight narrow facets were added- one to the edge of the pavilion and the table. Lodewyk (Louis) van Berquem was the first to introduced absolute symmetry in the disposition of facets. This Flemish polisher of Bruges cut stones in the shape known as pendeloque or briolette; that were pear-shaped with triangular facets on either sides. The culet was still missing as the bottom was left flat.
Brilliant cut emerged somewhere by the mid-seventeen century called Mazarins with 17 facets on the crown. Notable here, since burting had not yet developed the diamonds were not round but rounded squares. By 18th century emerged the cushion shaped old mine cut with 33 crown and 25 pavilion facets. The 19th century European cut was the improved and rounded version with a novel arrangement of facets.
Tolkowsky in 1919 gave a revolutionary turn to diamond cutting. In his book ‘Reflection and Refraction of Light in Diamond’, he manifested- Because every facet has the potential to change a light ray's plane of travel, every facet must be considered in any complete calculation of light paths. He suggested best proportions of a round brilliant diamond which results in the sparkling display of light and dispersion. Though the proportions provided by him are not perfect, yet they are the basis of all cut theories till date.
A diamond that has the top facet or "table facet" exactly perpendicular to the bottom of the diamond or "pavilion" and has its other facets precisely aligned with excellent symmetry, may show patterns that look like arrows from the top and hearts from the bottom. The stone needs to be viewed loose under a gem-scope to see the pattern. Although the hearts and arrows property is indicative of a top-tier cut, it does not always mean the diamond will be the most brilliant. Optimal facet placement is the key to brilliance and more important than facet patterning. Not all ideal round cuts will have the hearts and arrows effect either.
It is one the most famous cut and is used to maximize the brilliance of the diamond. The modernistic round brilliant has a perfectly rounded girdle with 57 facets or 58 if the culet at the tip is included; 33 on the crown and 25 on the pavilion. The girdle may be frosted, polished smooth, or faceted. Now a days most girdles are faceted with 32, 64, 80, or 96 facets (these facets are excluded from the total facet count). Some diamonds may have small extra facets on the crown or pavilion created to correct the flaws. The Princess Cut
The Princess cut is the second to brilliant cut in terms of popularity accenting heightened diamond fire. Square shaped resembling a pyramid; it is one of the modern diamond cuts, evolved around 1970s. Typically the diameter of the princess cut is smaller than that of a brilliant cut preserving the carat weight, but the length is longer. The princess cut is also referred to as square modified brilliant, as it amalgamates the brilliance of a round cut with facelook of square or rectangular appearance. There is one downside though, princess cut diamonds have lesser brilliance compared to the brilliant cut. Step cuts
Step cut diamonds have oulines either rectangular or squarish and whose facets are parallel to the girdle, almost rectangular. Possessing an octagonal outline most of these stones have their corners cut short, giving appearance of an emerald cut. With the crown and pavillion safely shallow-step cut these diamonds score points in accentauting clarity, whiteness and lustre. Rose cuts
A basic rose cut shows a flat base and triangular faceted crown. They have circular oulines and are most seen in the antique jewelry. Variations of rose cut are: the briolette (oval); Antwerp rose (hexagonal); and double Dutch rose (matching two rose cuts joined back-to-back).
The choice of the diamond is not according to any fancy discretion. It depends upon the original shape of the rough stone, the internal flaws, the carat weigh that you want to retain, not forgetting the popular trend. The cutter must consider different variables before deciding on the cut of the diamond.
For example, it is easier to cut a rough diamond into brilliant round cut as you can obtain two stones with minimum loss of carat weight. If there are more inclusions present then diamond deserves a fancy cut. Brilliant cuts have requisite proportions that would see high weight loss; nevertheless, the fancy cuts are much more pliant in this view.
The cutters can at times choose lesser proportions and symmetry, to debar inclusions or to conserve carat weight. The per-carat cost of diamond is much more if the stone is more than one-carat weight. While the round brilliant cut is believed touchstone for diamond, with its proportional shape and symmetry, the option of fancy cut is determined heavily by what is in vogue.
While selecting cut for the large diamonds the most important criterior considered is how well the cut will reflect the diamond properties from all angles. In moderate size diamonds, the cut is prefered for its face value.
To summarize the choice of cut should result in the following results: a. Maximizing Value
The process of cutting should result in the maximization of the finished diamond cost. To maximizing, the value of finished diamonds, from a rough diamond into a polished gemstone, is both an art and a science, based on mathematical calculations and cutters expertise. The choice of cut is influenced by many factors. The popularity of certain shapes amongst consumers largely influences the decision of the cutters. Proportionate symmetry, removal/correction of flaws, burting, polishing all result in the maximizing the diamonds value. However, the basic physical factors calls for retaining the original shape of the rough stone and elimination of flaws. b. Weight retention Weight retention is the most important factor to be taken care of while cutting the diamond. The market factors display an exponential increase in value of diamonds as weight increases. Surely, the cut cannot increase the weight of the diamond but a good cut can retain the maximum size. The weight retention analysis studies the rough diamond to find the best combination of finished stones as it relates to per carat value. For instance, a 2.20-carat (440 mg) octahedron may produce either two half-carat (100 mg) diamonds, whose combined value may be higher than that of a 0.80 carat (160 mg) diamond and 0.30 carat (60 mg) diamond that could be cut from the same rough diamond.
The round brilliant cut and square brilliant cuts are preferred when the crystal is an octahedron, as often two stones may be cut from one such crystal. Oddly shaped crystals, such as macles are more likely to be cut in a fancy cut—that is, a cut other than the round brilliant like pear, marquise etc.
The diamond needs the planning and experience of the master cutters to give it a mesmerizing appearance. The diamond cutting process involves thoughtful- planning, cleaving or sawing, burting, polishing, and final inspection. Planning Before cutting the diamond, the manufactures need evaluate the rough diamond from the economic point of view as well. Apart from concentrating on getting the product to the market faster, the decision should also get them maximum return on investment. The updated technology today allows them to derive a 3-dimensional computer scanned model of the rough stone. The photographed the inclusions are then viewed against the scanned model. The entire process allows them to calculate the best cut and process for the diamond. While a certain cutting plan may yield a better value, a different plan may yield diamonds that will sell sooner, and thereby returning the investment sooner Cleaving or sawing
Every bit of the diamond crystal is valuable, even the dust. Cleaving is the separation of a piece of diamond rough into separate pieces, to be finished as separate gems. The manufacturer can also gain some cost by selling the these smaller pieces. Sawing refers to the usage of a diamond saw or laser to cut the diamond rough into separate pieces. Bruting
Bruting is the process whereby two diamonds are set onto spinning axles turning in opposite directions, which are then set to grind against each other to shape each diamond into a round shape. This can also be known as girdling. Polishing Polishing is the name given to process whereby the facets are cut onto the diamond and final polishing is performed. The process takes the steps blocking, faceting, and polishing. Final inspection The final stage involves thoroughly cleaning the diamond in acids, and examining the diamond to see whether it meets the quality standards of the manufacturer. A good polished diamond is clear without any visible blemishes on the surface. The execution of the diamond cut, shape, and polish with proper precision go hand-in-hand in giving diamond its final finish. Diamond Cutting Tools
Many varieties of tools are used to execute the diamond cutting process. They can be customized to perform singular jobs, such as faceting, drilling, angle cutting, shaping, metal removing etc. For example, router bits are the rotating tools that are employed with the routers to shape the edges of the diamond. There are different types of cutting tools available in hundreds of shapes, sizes, for intended usage.
Angle Cutters – these are milling cutters with their cutting face angled in relation to its axis of rotation. They are typically used in machine applications.
Boring Tools – used to cut or finish the inner diameter of drilled holes.
Router Bits – rotating tools that come in a wide variety of shapes and are used with routers to shape edges.
Drill Bits – rotary cutting tool used to drill holes.
End-mills – similar to a drill bit, it is used in industrial milling applications and made of high speed steel or tungsten carbide.
Broaches – used for the precision sizing and finishing of material surfaces.
Grinding Wheels – used for finishing, shaping, and metal removal.
De-burring tools – removes sharp metal splinters, burrs, flashing and other rough finishes left by cutting and machining.
Fly Cutters – similar to a lathe tool, but mounted in a special holder. Uses one or more single-pointed tools to plane a surface.
Abrasive Saw Blades – cutting devices used with saws and other hand-held cutters.
Knife Blades – industrial class tools used to shear and cut metal, primarily using the force of pressure to make a cut.
Turning Tools – used on lathes for finishing the outside diameter of a piece of material.
Countersinks – cut angled holes into a piece of work material.
Make sure you always buy diamonds from a reputable jeweler and ask questions about diamond characteristics. Thoroughly inspect the stone and checks if it does not have a-
A broken or chipped culet.
A missing culet or one that's off center.
Misaligned or extra facets.
A girdle that is too thick, creating poor proportions, or too thin, making it easier to damage.
A fringed girdle, with tiny cracks going into the diamond.
A table that slopes to one side.
The proportion of the crown angle with respect to the pavilion angle has the biggest outcome on the diamond look. More or less, steep pavilion angle can be equilibrated by a shallower crown angle, and the other way around. Many certificates do not grade the diamond cut properly. The cut significantly affects the diamond value so you must see that a trained person has rated the diamond cut properly. Did you know?
India is the world's top diamond cutting and polishing center processing 11 out of 12 diamonds in jewelry worldwide. The sector employs 1.3 million people and accounts for 14% of India's $80 billion of annual exports. India’s share in the world polished diamond market is 92% by pieces and 55% by value.
Only 0.01% diamonds available are above 1.00 carat no wonder they are so expensive.
Most diamonds fluorescents when viewed in darkness.