Diamond Cut…The Basics: Step 1 – Understanding diamond “certs”
Chapter 2

If you are going to purchase a diamond, and know what you are getting when you purchase it, you need to be able to understand the information that is presented on a “lab grading report”, and how the information was obtained. Having this knowledge will further assist you to know if any follow up/independent data, presented to you by the jeweler, in conjunction with a “lab grading report”, is valid and accurate.

Here are several examples of “lab grading reports”. To gain a better understanding of how information is broken down on a lab report, we will examine one line by line.

NOTE: We will not be discussing the relevance of this information to the diamond’s cut quality, as that will be done in detail later on in this tutorial.

GIA Lab Grading Report
Figure 2.1

EGL USA Lab Grading Report
Figure 2.2

For the purposes of this tutorial, we will examine the AGS Lab Grading Report. Most reports have similar information on them and are simply arranged differently. Immediately below is the full copy of the “lab grading report”. Since the lettering on this report is quite small, we have included enlarged portions of the report below that will allow us to examine the information contained in this report more closely.

AGS Lab Grading Report
Figure 2.3

Figure 2.4

Figure 2.5

Figure 2.6

If we examine Figure 2.4, we see that this area of the report displays the basic information about the diamond. Let’s break this down point by point

•    Shape and Style

o    Simply stated, the shape and style of the stone…in this case Round Brilliant.

•    Measurements

o    These are the measurements of the diamond in millimeters. The three numbers that make up the measurements given on the report are the 1) Maximum diameter of the stone, 2) Minimum diameter of the stone, 3) and the Depth of the stone. The diameter is the width of the stone as measured through the girdle. The Depth is the distance between the Table Facet and the Culet. NOTE: The average diameter measurements are very important, as most measurements expressed in percentages on a “lab grading report” are based on the average diameter measurement.

•    Cut Grade

o    This is the section that deals with the overall cut grade given by the laboratory grading the diamond. Different laboratories grade diamonds differently…these different grading methods will be discussed in detail later on in this tutorial.

o    On this report we can see the different categories…

•    Light Performance

•    This is the grade given to this diamond based on how it performed in the light reflection, brilliance, and other light performance analysis that it was subjected to during the grading process.

•    Proportion Factors   

•    In addition to testing diamonds for light performance, this laboratory also applies strict proportion standards to diamonds. It takes into account measurements such as depth, table, crown angle, pavilion angle, and minor facet measurements. The grade given to each diamond in this section is based on how well each of these measurements fit into the ranges prescribed by the grading laboratory.

•    Finish

•    Finish is comprised of two separate and distinct factors, polish and symmetry.

o    Polish

•    Polish is exactly what it sounds like…it is the polish work on the outside of the stone. After a cutter finishes the cutting and shaping of the diamond, he must polish the diamond to remove the marks made during the cutting of the stone, and give each facet a clear and highly reflective surface. This polish is graded on each facet, and only diamonds with exceptional polish across the whole diamond can receive the laboratory’s highest grade.

o    Symmetry

•    Symmetry is a factor that receives a lot of attention. There are different kinds of symmetry that pertain to a diamond, and it is important to understand each one, as they are completely different and affect the diamond in totally different ways. The symmetry that is graded on the lab report is the external symmetry of the diamond. It takes into account factors such as facet point alignment, table centering, facet alignment, consistency of facet shapes, etc.

•    Color Grade

o    This section deals with the color of the gem. Color is discussed in Emma Parker & Co.’s Diamond Tutorial. For questions about color, please refer to that tutorial.

•    Clarity Grade

o    This section deals with the color of the gem. Clarity is discussed in Emma Parker & Co.’s Diamond Tutorial. For questions about clarity, please refer to that tutorial.

•    Carat Weight

o    This section deals with the color of the gem. Carat weight is discussed in Emma Parker & Co.’s Diamond Tutorial. For questions about carat weight, please refer to that tutorial.

NOTE: A very important fact to understand about Color and Clarity is that the grading standards vary widely from on grading laboratory to another. Some of have much stricter standards than others, and this is something that should be carefully considered before purchasing a diamond.

Looking at Figure 2.5, we can see a proportion map of the diamond, with basic proportion and measurement data. The first thing that we notice when looking at this, is that the only two standards of measurements used are Percentages and Degrees. The very first measurement of the diamond is the 100%, which is equal to the average diameter of the stone at its widest point, the girdle. It is based off of this percentage that all of the other percentage measurements are calculated.

Directly under this measurement, we can see the 55.4% measurement. This is the diameter of the Table Facet, expressed in a percentage of the total average diameter.

The vertical line along the left had diamond is the measurement of the Total Depth of the diamond, again, expressed as a percentage of the total average diameter, in this case, 61.9%

The vertical line along the right side of the diamond, broken into three different measurements essentially breaks down the factors that make up the total depth of the diamond. These three factors are called Crown Height, Girdle Thickness, and Pavilion Depth.  In this case you can see the three measurements are as follows.

•    Crown Height – 15.5%
•    Girdle Thickness – 1.6% to 4.4%
•    Pavilion Depth – 42.8%

The two angle measurements on the left hand side of the graph are the Crown Angle and Pavilion Angle measurements. In this case, the Crown Angle is 34.8 degrees, and the Pavilion angle is 40.6 degrees.

The two numbers in the diamond represent facet length measurements.  The measurement in the small facets on top is the Star Facet Length, and the measurement in the slightly larger facets on the bottom is the Lower Girdle Facet Length. For this diamond, the Star Facets measure 51% and the Lower Girdle Facet’s measure 75%.

It is very important to understand that these two percentages are not calculated against the total depth. Rather Star Facet Lengths are expressed as a percentage of the total distance between the edge of the Table and the edge of the Girdle. Lower Girdle Facet Lengths are expressed in a percentage of the total distance between the Culet and the edge of the Girdle. (See illustration below)

Star Fact Measurement
The Green arrow, in Figure 2.7, represents 100% of the distance from the edge of the TABLE to the edge of the GIRDLE. The STAR FACET measurement is expressed as a percentage of the total measurement.

Figure 2.7

Lower Girdle Facet Measurement
The green arrow in Figure 2.8 represents 100% of the distance between the edge of the GIRDLE and the CULET. The LOWER GIRDLE FACET measurement is expressed as a percentage of the total measurement.

Figure 2.8

Lastly at the bottom, we see the Culet Size. This is almost always expressed as a word. Culet sizes vary including sizes of None, Pointed, Very Small, Small, Medium, etc.

The last graphic we see, Figure 2.6, is the Clarity Plot of the diamond. This is where the grading inclusions, that were visible at 10x magnification, are plotted by the grader. Clarity has already been discussed in brief in the Emma Parker & Co. Diamond Tutorial, however there are some simple hints to help you spot important information on the Clarity Plot. All inclusions plotted in RED INK are INTERNAL inclusions. All inclusions plotted in GREEN INK are EXTERNAL inclusions.

This basic walk through of the information that is listed on a lab grading report will give you a good foundation in what information you will be presented with later on in this tutorial, and what each measurement relates to. In the following chapters we are going to dig deeper into cut, what to look for in a great cut, what tools and reports are useful in looking for a good cut and how to read them, and more.

Written by Timothy Andre, Emma Parker & Co.     www.emmaparkerdiamonds.com

Diamond Cut…The Basics: Step 1 – Understanding diamond “certs”
Chapter 1

You have done it…you have made the decision to step out, take the leap, and buy a diamond. Diamonds, unlike most things that we buy in our lifetime, are items that most of us don’t think about on a regular basis. Unlike stereos, cars, televisions, computers, games, and other mass produced, branded items that we purchase, diamonds are individually unique, fundamentally altered but not manufactured, and subjectively reviewed products.

For example, if you want to purchase a car, you can research the car, read user feedback, professional evaluations, test drive results, trade publication reviews, and more. You can even take one of the cars out for a test drive at your local dealership. Every car of that class is built exactly the same, and although it may yield a slightly different experience to each person that purchases it…its commonalities will overwhelm its differences because all of the cars have been produced using identical parts, manufactured for that specific purpose, and each car has been assembled according to a standardized template.

In contrast, diamonds differ in three specific ways from the average consumer product.

Diamonds are individually unique

Diamonds are mined out of the ground. No two diamonds that are mined are the same. This concept seems basic, however the differences are massive from diamond to diamond. Consider that each diamond is a different size, weight, different shape consisting of a different number of sides or flat surfaces…with each flat surface having a different size, shape, and angle of orientation. In addition, each diamond has different inclusions, cracks, strong points, weak points, molecular crystal structure, color, etc. The difference in characteristics from diamond to diamond is absolutely massive.

Diamonds are fundamentally altered but not manufactured

It is critical to remember that, unlike mass produced products, which are built using identical parts and designed from a master template, diamonds are not manufactured…they are simply altered from a rough state to a finished state using a number of methods, tactics, and devices. Often times finished diamonds have been compared to artists paintings, however this is a poor comparison, since an artist starts with a blank white canvas and all the primary colors. His freedom to create is unlimited, there is no science that will judge the quality and performance of the artists finished painting. In truth, there is nothing that can be compared to the task of transforming a rough diamond into a finished product. A cutter, wishing to take a rough diamond, and transform it into a finished diamond must take the following things into consideration:

He is not working with a blank canvas

The rough diamond is the cutter’s canvas, and he must abide by the laws, restrictions, and unique idiosyncrasies of the diamond rough that he is cutting.

He does not have freedom of creativity

The diamond cutter does not have the freedom of creativity for several reason, the first of which is that, the value of his canvas is determined by its weight, however, in order to unlock the beauty within the rough diamond, he must cut a pattern into the stone, thus causing the rough diamond or “canvas” to loose weight; i.e. value. However, the “cut” of the stone will bring value to it, so the cutter is left to maintain a delicate balance between the value of the weight vs. the value of the cut, making sure that the quality of his cutting does not suffer in an effort to retain weight, nor does he cause the rough, his “canvas”, to suffer undue weight loss as a result of his cutting.

His finished product will be subject to scientific scrutiny

Because diamonds are geometric objects which are designed to reflect light, science can be, and is applied to judge the quality of diamond cutting. This application of scientific and mathematical principles to the analysis of diamond cut quality has lead to the formation of “diamond cut grades” by gemological laboratories around the world. These grades relate directly to a diamond’s visual beauty, which relates to the diamonds consumer appeal, which furthermore relates the demand for the diamond, thereby causing the “cut grade” of the diamond to directly impact the diamond’s value. All of this serves to put the diamond cutter in a box, forcing him to take a predetermined canvas, with its unique restrictions, and produce a product that must fall within a scientifically defined box, while balancing the value of weight vs. cut, both of which are diametrically opposed to each other throughout the cutting process.

Diamonds are subjectively reviewed products

Since diamonds are each so individually unique, there can be no “generalized” grading system, or standardized review system for the cut of diamonds. While it is completely feasible for a critic to write a review on last years model of the BMW 325i…it is utterly impossible for an individual to write a review that will apply to more than one diamond in the world. This vast diversity from diamond to diamond has forced the creation of a set of parameters that attempt to encompass a broad range of proportions and measurements, which all yield similar results, and categorize them as yielding a certain “grade”. These multiple sets of parameters have been defined by different gemological labs around the world, with each set having its own unique interpretations derived from its own scientific processes, and presented to the consumer with its own verbiage and persuasive argument for why it is the most grounded basis for grading.

The reason that it is so important to understand that uniqueness of diamonds, the difficulty with which the cutting process is fraught, the immense variation in cut grading, and the application of scientific tests, is that this understanding is imperative to gaining a full comprehension of diamond “certs”, how they are produced, and why there are so many conflicting opinions in the industry.

The diamond “cert” as it has become known, is in actuality, not a certificate, as the name would suggest, but is rather a report issued by the gemological laboratory that was paid, by the diamond’s owner, to grade the diamond. The report, commonly called the “cert” (this will be referred to as a “lab grading report” for the remainder of this tutorial), is a printed record of the gemological lab’s determinations as to the quality of the diamond. The findings, although based on a scientific grading system, are really a codified representation of a subjective grading analysis that was performed by one or several human graders, each subject to their own grading style and grading predispositions.

Each gemological laboratory has its own individual grading process, that stems off of its unique grading protocol, using its own predetermined course of grading procedures, and employing its own preselected scientific equipment for testing and observing the stone in question.

The fact that there are many different gemological laboratories, each with its own grading system, has lead to a wide variety of “lab grading reports” being issued on diamonds, and presented to the general consumer as absolute fact about the quality of the diamond being purchased.

Of course, at this point, the question must be asked…why are there so many standards…and why has no single standard been determined?  The answer is quite simple. Most consumers, when presented with a “lab grading report”, are wiling to take the information being presented about the stone at face value, many times with little or no knowledge about the gemological laboratory, its grading practices and procedures, or its reputation in the market place. This action by consumers, and the fact that retailers are aware of this fact, has lead to a very simple, yet very detrimental trend in the diamond grading industry.

Consider this…if the average consumer takes a “lab grading report” at face value, without regard to the quality of the grading performed by the lab; and the value of a diamond rests almost entirely, excepting its weight, on areas of subjective grading; i.e. cut quality, color, and clarity; a lab that grades on a loose standard (issuing reports that give diamonds a slightly better grade than the lab’s stricter competitors would give) would allow retailers to present a “lab grading report” that is more “favorable” as well as giving them the ability to charge a higher price for a lower quality stone. The main basis for many labs that grade based on loose criteria is that of consumer ignorance. Diamond cutters, wholesalers, and retailers use these labs to grade their diamonds in an effort to increase the value and salability of their inventory, with the by-product of this effort being added expense to the consumer.

It is imperative that, as a consumer, you have a solid understanding of the major gemological laboratories in the market, their grading systems, and their reputations for the accuracy of the “lab grading reports” that they issue.

Below is a short list of the major gemological laboratories, in the basic order of their grading strictness.

NOTE: It is important to remember that diamond grading is done by humans, which means that human error is a possibility. It is possible for any gemological laboratory to make a mistake in the grading of a diamond.

Diamond Grading Laboratories

•    American Gemological Society Laboratory (AGSL or AGS)
•    Gemological Institute of America (GIA)
•    Gem Certification and Assurance Lab (GCAL)
•    HRD Antwerp
•    European Gemological Laboratories USA (EGL USA)
•    European Gemological Laboratories (EGL)
•    European Gemological Laboratories Israel
•    International Gemological Institute (IGI)

Written by Timothy Andre, Emma Parker & Co.     www.emmaparkerdiamonds.com

Diamond Cut: The Basics – Understanding Technology
Chapter 3

In order to understand the different measurements, tests, and evaluations that diamonds are put through, and what the results of these test mean to the diamonds visual performance, it is necessary to first have a solid grasp on the technologies and techniques used to gather this data.

There are many different tools that are used by gemologists and diamond graders to determine facts about a diamond’s properties. This section is going focus mostly on the more complex and less understood tools, and is also going to focus mostly on tools used to determine cut and light performance.

Non-Contact Scanners

The Sarin machine is the most popular device in a small group of machines called “non-contact measuring devices”. These tools are, in essence, scanners that scan the outside surface of the diamond and measure all the flat surfaces of the stone. They do this by taking many 2 dimensional images of the diamond’s silhouette, and from these images, constructing a 3 dimensional model of the diamond, complete with measurements, that is able to be manipulated by the gemologist. Basically the Sarin is able to reconstruct the diamond in a virtual world with extreme accuracy.

This is extremely useful for gaining measurements on the diamond, examining the cut of the diamond, determining angles, and more. In addition, the computer software is able to simulate light sources, thereby allowing the gemologist to subject the diamond model to different types of light, at different strengths and from different (single or multiple) angles, and more. This allows the diamond to be analyzed scientifically in a completely virtual realm with astonishing accuracy. The data gained from this analysis is very useful in determining the quality of the diamond’s cut, and hence, its ability to reflect light.

Similar scanners to the Sarin are the Helium Scanner and the OGI Scanner. At Emma Parker & Co. we use the Sarin.

Reflector Devices

A simple yet critical set of tools that is used to study and critique a diamond’s cut and light performance are the “reflector devices”; the most well known of these devices is called the Ideal Scope.

The premise of these tools is quite simple; they show the light that is being reflected by the diamond in a form that is visible to the human eye. This allows a person to observe “light return” vs. “light leakage” in a diamond easily.

Having read the Emma Parker & Co. Diamond Tutorial, you should have a solid grasp of the function of the Ideal scope and other devices such as the AGSL ASET reflector. If you have not yet read the Emma Parker & Co. Diamond Tutorial, please stop here and read that in its entirety before continuing on, as it will be necessary in order to understand the upcoming chapters of this tutorial.

DiamCalc Software

The DiamCalc Software is a wonderful program that is designed to take the diamond models that are generated by a “non-contact measuring device” and put them into a visible model that can be manipulated in a plethora of conditions, angles, lighting, and so on.

It can even take the diamond models and simulate them under “reflector devices” such as the Ideal Scope, ASET, Firescope, and more. This program is able to “skin” the diamond, if you will, with a visual appearance that is very similar to the real life diamond.

One of the strongest features of this program is that it allows the user to enter different parameters for the diamond. For example, if we know that a diamond with proportion set 1 looks good, but we want to see what would happen if the table was a different size, we can change the table in the program, and see the effects of this change on the diamond, both visually, and through a reflector device. This is an incredibly powerful tool for research and demonstration.

GEMEX BrillianceScope

The BrillianceScope was designed to measure the light return/optical performance of a diamond in direct light. The technology is actually a very simple and logical design.

Have a look at Figure 3.1

Figure 3.1

This is a basic diagram of the inner workings of the GEMEX BrillianceScope. The diamond rests on a circular piece of glass.  The cover over the diamond is then closed, creating a completely white environment surrounding the diamond. (See Figure 3.2

Figure 3.2

Courtesy of GEMEX

Light, generated by a fiber-optic ring light is then projected up, through an opening in the white half-sphere, through the glass, into the top of the diamond, as illustrated in Figure 3.1.

The light moves to 5 specific sets of three individual points, stopping briefly at each of the 15 points. For each set of points, a camera, at the bottom of the machine, aiming up through the center of the ring light, triple exposes an image of the diamond, one picture at each point in the set, “laid” one on top of the other, as it were.

Once these images are captured and stored, the software breaks down each image on a pixel by pixel basis, and looks at three distinct items.

1. The amount of White Light being reflected by the stone. This will account for brightness or brilliance to the viewer’s naked eye.

2. The amount of Colored Light being reflected by the stone. This will account for the fire or rainbow colored light to the viewer’s naked eye.

3. The “movement” of light within the diamond, otherwise called Scintillation. This will be seen as sparkle to the viewer’s naked eye.

These results are then compiled, and compared against a controlled database of diamonds that have been tested on the machine, and the results of these tests form the basis for the “grading by comparison” system used by the GEMEX software. The result is a report like the one pictured below.

Figure 3.3

Courtesy of GEMEX.

The results of the GEMEX report, displayed above in Figure 3.3,  are heavily curved; i.e. meaning that from the bottom of the chart to the middle of the “HIGH” grade encompasses up to the 85th percentile of all diamonds tested, while grades from the middle of the “HIGH” mark to the end of the scale at “VERY HIGH” comprise the 86th – 100th percentile of all diamonds tested.

The GEMEX is an interesting tool, and is useful to a point for gaining a perception of how a diamond will perform in direct lighting conditions, such as direct sunlight, direct spotlighting, etc.

The GEMEX is limited by the fact that its results only apply to direct lighting, and that its “grading by comparison” system is a totally subjective grading system which, by its nature, will always be subject to any influences that affected the block of results from the control group upon which the entire basis of the grading schematic rests.

Another drawback to the GEMEX is that results can be manipulated slightly by a crafty user. Something as simple as placing a finger print smudge on the top of the diamond can cause a much higher rating on the White Light performance than the stone would have if it were totally clean. Meticulous cleaning of the diamond and the glass is absolutely necessary to ensure a proper scan. GEMEX inspects each scan before a report is issued and will reject reports that show excessive dirt or smudging, however the ease with which results can be manipulated remains a draw back in our opinion.

Having an enormous amount of experience with the GEMEX BrillianceScope, both as a selling tool and as an analysis tool, I do believe that the technology is by enlarge sound, and the results valid. I have also found that consumers place far too much importance on the report, and often find themselves crippled with “analysis paralysis” and the fear that they should be waiting for a diamond that scores “the perfect 10” on the BrillianceScope, while letting world class diamonds go by on a technicality from a subjective, computerized, “grading by comparison” system. This is foolish and should be avoided. It is important to consider all aspects of a diamonds performance when purchasing a stone. To do this, one must consider a full body of analysis, of which the BrillianceScope is an informative, albeit non-essential piece.

ISEE2

Figure 3.4

Courtesy of ISEE2 Diamonds

The ISEE2 machine is another technology that measures a diamonds Brilliance, Fire, Scintillation, and Symmetry in a controlled light setting using mainly diffused light. The inventor of the ISEE2 states that the machine subjects diamonds to 48 different lighting conditions. The ISEE2 takes 15 images a second, and analyzes these images, breaking them down to analyze White Light, Colored Light, Light Movement (Scintillation), and Optical Symmetry (the pattern cut into the stone, in this case the machine is looking for the hearts and arrows pattern that is most commonly displayed in a properly cut 57 facet, traditional pattern round diamond).

Having extensively used the ISEE2 machine for both the sale and analysis of diamonds, I can say that the results of the ISEE2 are consistent with other technologies, and are valid for consideration, provided that they are not overly weighted by a consumer in making their decision.

As with the BrillianceScope, the rating system used by the software program is proprietary and unknown to anyone other than the developer. As with the BrillianceScope, this would not normally be a reason for concern, as the results have been shown to coincide with scientifically established measurements for “ideal light performance”, save for one critical piece of information; the ISEE2 machine was developed by the manufacturer of ISEE2 Diamonds specifically for the sale and marketing of their own ISEE2 Branded Diamond, which is a 57 facet Ideal Cut Hearts and Arrows Diamond.

This fact does not invalidate the ISEE2 as a technology, nor yield its results as void, it merely casts a rebuttable shadow of doubt on a technology that has tested positively in private lab tests with both ISEE2 Diamonds and non-ISEE2 diamonds. The problem lies within the subjective “grading by comparison” standard that is employed by the software, which is proprietary, and therefore not discernable by consumers. So far, independent testing, including my own extensive use of the ISEE2 seems to show that the grading put forth by this technology is consistent and relatively accurate when compared to the current positions, in regards to cut, of the major gemological laboratories, such as GIA and AGS.

As with the Brilliance Scope, the ISEE2 is an interesting, albeit non-essential source of information that can be considered when purchasing a diamond. The most prominent danger posed by this technology is the overemphasis that is often placed by the consumer on the importance of its results.

GIA Diamond Dock

Figure 3.5

Courtesy of GIA 

The GIA Diamond Dock is a lighting source that is used to evaluate diamonds. (Figure 3.5) This lighting environment is intended to simulate true “daylight” as closely as possible. Using a combination of diffused fluorescent lighting and L.E.D. direct lighting, it is able to simulate daylight fairly accurately.

This is very useful for observation, photography, and “naked eye” light performance analysis of a diamond.

The Diamond Dock also doubles as a color grading environment.

TECHNOLOGIES THAT DO NOT PRETAIN TO “CUT GRADE ANALYSIS”

Traditional Jeweler’s Triplet Loupe

Figure 3.6

Courtesy of Kassoy.com

A traditional jewelers “triplet” loupe is a simple tool that you will find in almost any good jewelry store. This is a simple, hand-held magnifying lens that allows a viewer to inspect the diamond under magnification fairly easily and in almost any location and situation. The standard magnification for these loupes is 10x, however different loupes are available for 20x and 30x as well.

This particular kind of loupe is referred to as a “triplet” because the magnifier is actually made up of three different lenses in order to provide the highest clarity to the viewer.

At first, using a loupe can be tricky, however with a little bit of practice, it is possible to gather a vast amount of information about a diamond simply by taking a good, long look at it through a loupe.

High Power Microscope with High-Definition Camera

Figure 3.7

Courtesy of Kassoy.com

A good source of high magnification is critical to the proper analysis of any diamond. While observing a diamond through a 10x triplet loupe is good, having the ability to zoom in to 50x or 60x magnification allows a jeweler to learn much more about a diamond and its imperfections, as well as its cut. In addition, having the ability to share this information with a customer is vital to ensuring that the customer feels confident in the diamond they are looking to purchase.

At Emma Parker & Co., we use the microscope pictured above. It is a 50x magnification microscope, with glass lenses produced by the company Leica, a leader in the optical glass industry. The microscope also has a high definition camera mounted on it, through which images of inclusions can be taken, and live video of the magnified diamond can be streamed.

The pictures taken by this microscope allow customers to see, in remarkable detail, the characteristics of the diamond magnified. See examples below…

Figure 3.8

The red arrows point to the “grading inclusions” in the diamond. These are the imperfections that contributed towards the diamonds clarity grade, as given by the grading laboratory, such as GIA or AGS.

At Emma Parker & Co., we point out these inclusions with red arrows in a picture taken under the microscope so our customers can easily locate the incusions in their diamonds.

Colorimeter

Figure 3.9

Courtesy of Kassoy.com

In today’s advanced technological market, advanced and accurate tools have emerged for determining the color of a diamond. The tools, called “colorimeters” have advanced to such a point that they are quite accurate and sophisticated. These are fantastically costly machines, and are not used by everyone in the industry.

Like many of our fellow colleagues, we here at Emma Parker & Co. prefer the old fashion way of color grading, the way that GIA and AGS still use to grade diamonds, a white tray, a color grading light, and set of master stones.

We feel that some things are better left to the human eye and trained observation.

Written by Timothy Andre, Emma Parker & Co.     www.emmaparkerdiamonds.com

Diamond Cut: The Basics – Cut, Part 1 – Facet Structure
Chapter 4

Having a well-grounded understanding of a diamond’s facet structure is critical to gaining a full understanding of cut. In this chapter, we are going to breakdown the facet structure of a round diamond and discuss the basic purposes of the facets of the diamond. In the following chapters, we will be taking each shape, with its unique facet structure and discussing it, its cut, what measurements, angle combinations, and facet lengths bring out the stone’s beauty.

THE CROWN

The Table Facet

Figure 4.1

The table facet is the largest facet on the diamond. It is common to all main-stream shapes (Round, Square, Cushion, Pear, Marquise, etc.), and cut patterns produced in the market. The major function of the table facet is to allow light to enter the diamond through the top. Since a diamond’s sparkle is actually light that is being reflected up out of the diamond, it is critical that large amounts of light be able to ender directly into the diamond. In order to allow a maximum amount of light to enter the stone directly, a large, flat facet on the top of the diamond is essential.

The “perfect” table size has been a topic of fierce discussion and debate between experts over the years, with each side being deeply entrenched in their own opinions. As with many areas of diamond cut, many of the experts’ positions overlap, showing that there is a certain amount of veracity and consistence to each of their arguments. Rather than to take a stance with any one school of thought, we prefer to look at the intersection of the major, scientifically supported theories.

There is no “one size fits all” when it comes to table measurements. Each one is unique in the way that it interacts with the other measurements around it, and certainly, from shape to shape, proper table measurements take on totally new ranges and rules.

We will be looking closely at optimal ranges for table measurements a little later on when we break down our discussion of cut for each different major diamond shape on the market.

Something that is very important to remember, not just with the table facet but with all facets on a diamond, is that they live in a 3 dimensional world and can move in multiple directions.

Most often, when a facet’s measurement is discussed, we talk about its diameter, depth, length, or angle. However, a facet can “move” in other ways that need to be considered. For example, is the table off-center? Is the table tilted, in relation to the girdle of the stone? Is the table warped, or skewed? Is the shape of the table symmetrical? Is the facet pattern of the stone symmetrical? Are the facets on the pavilion and crown lined up with each other? Is the culet off-center? Is a facet shifted, twisted, rotated, beveled, curved, etc. While this is a topic that we will not be touching on again until later, it seemed fitting to mention it here in order to set the tone for discussions to come.

The Star Facets

The star facets are small, triangular facets that surround the table, in stones that exhibit the “brilliant cut” pattern, such as rounds, ovals, pears, hearts, marquise, princess, radiant, etc; as opposed to a step cut pattern, such as an emerald or asscher; or even a proprietary cut, such as a Lucida, Criss-cut, etc (we will address their facet structures later on). See figure 4.2.

Figure 4.2

The stars are the first of three sets of facets that make up the angled portion of the diamond’s crown. Light that enters these facets will be bent as it passes through them, in contrast to light that enters through the table. See figure 4.3 and 4.4. (These illustrations are of a diamond cut to AGS Ideal proportions, using a single “ray-trace light source” in the model to illustrate the path that light takes through the stone.

Figure 4.3

Figure 4.4

The facets that make up the crown of the diamond are very important, because they will bend light passing through the diamond in two way, when it enters the stone, and when it exits the stone. If these facets are cut to angles that are inconsistent or improper, it will have significant effects on the sparkle and brilliance of the diamond.

The most common measurement used to express the dimensions of a star facet is that of length, which is expressed in the percentage of the distance which the facet covers between the edge of the table and the edge of the girdle (this was already discussed in the first chapter of this tutorial).

Again, there are many schools of thought as to what is the optimal measurement. Rather than proclaim the perfect measurement, it is more informative to look at how different star facet lengths affect the diamond, and how their measurements, when combined with various measurements from the pavilion of the diamond, will yield different optical results, within in which it is possible to find differing appearances which may appeal more to one person than another. The result of such truths is that no one measurement is “the best”, but rather a range of measurements and combinations should be considered. We will breakdown the different measurements and combinations for each shape later on in this tutorial.

The Bezel Facets

The bezel facets are the major facets in the crown of a diamond with the “brilliant cut pattern”. It is the angle of these facets that is depicted as the “crown angle” on the lab reports. These are the largest facets in the crown, and have the greatest impact on the light performance of the stone. The bezel facets of a diamond are illustrated in Figure 4.5, shown below.

Figure 4.5

The important statistic to consider about bezel facets is their angle. Since they are the major facets of the crown, they impact the bending of light more than the other two facet groups on the crown.

The key to finding a diamond with a good or great cut is not in the in angle measurement of the bezel facets alone, but rather in the combination created by the angle of the bezel facets and the pavilion main facets (pavilion main facets will be discussed later in this chapter). It is this combination that will produce the bending and reflecting of light. If only one set of these facets fall into the proper range, the variance in the non-conforming set of facets will offset the other.

Focusing on good combinations and how this will affect the diamond’s ability to reflect light is key if you want to find a diamond that is going to have the “wow” factor.

The Upper Girdle Facets

The upper girdle facets are those facets that have one edge touching the girdle. In stones with a “brilliant cut pattern” especially rounds, these small facets can play a very big roll. See Figure 4.6.

Figure 4.6

There are two issues that can happen with these facets that can affect the appearance and beauty of a diamond. They will both be covered under the section discussing the cut of a round diamond. So you know to look out for these topics, they are called Painting and Digging. As with any other portion of diamond cut, these points are hot points of controversy and argument. We will thoroughly discuss these issues a little later.

THE PAVILION

The Pavilion-Main Facets

The pavilion-main facets, sometimes called “the mains”, are the major facets that extend from the culet of the diamond to the edge of the girdle. These facets are responsible for the majority of the light reflection from the pavilion of the diamond. It is the angles of these facets that will determine where the light that enters the diamond will be reflected.

Figure 4.7

The measurement used to define this facet set is an angle measurement. You can see this measurement represented on a lab grading report as the “pavilion angle”. This measurement is a very important one, and, particularly in rounds, a very small change in the angle can result in huge impacts to the visual beauty and sparkle of the diamond.

Again…as with the crown angle…there is no one measurement that is the “best”. It is all about the combination of the crown and pavilion angles, working together to produce beautiful optics. Of course, there are limits, and angle measurements within certain ranges that tend to produce the nicest diamonds.

As we move through the coming chapters on cut, we will examine different shapes, and how changing the angles of the pavilion-main facets can affect the performance and beauty of a diamond.

The Lower Girdle Facets

The lower girdle facets, as their name would suggest, and just like the upper girdle facets, are the facets that extend from the edge of the girdle, down towards the pavilion. They are found in between the pavilion main facets and are grouped two together.

Figure 4.8

The primary measurement used to describe the lower girdle facets is that of length, expressed in a percentage…which is the percentage of the distance the facets cover between the edge of the girdle and the culet.

Their length is significant, as it can affect the visual beauty and appearance of a diamond, although their effect is not as great as the “pavilion mains”. Also…like their opposites (the upper girdle facets), lower girdle facets can also suffer the affects of Painting and Digging…which we will discuss later.

The Culet

The culet is the point at the bottom of the pavilion. The purpose of the culet is really to keep the diamond from being damaged on the bottom. Today, it is most common to see culets that are referred to a “None” or “Pointed”, since most diamond are brought to a sharp point at the bottom. This was not always the case however. Particularly in more antique cuts, it is quite common to see culets that are flattened, creating another facet on the bottom of the diamond.

The issue caused by having a large girdle is that it creates a facet that is parallel to the table. This opens an exit point for light to pass through at the bottom of the diamond, which allows light to pass directly through the diamond, without being reflected back to the viewer, i.e. “light leakage”.  Although the look of a large culet can be very enticing, especially in an antique stone, it is important to understand that it will allow a fair amount of light to be lost through the bottom of the stone, and will affect the overall light return of the diamond.

It is important to remember, once again, that diamonds are personal, and that something that one customer may consider undesirable, could be sought after and prized by another.

The Girdle

The girdle is the thin “band” around the widest part of the stone. The girdle is very important to the cut of a diamond, but not so much in the way of light performance. Rather, the girdle has to do with the structural soundness of the diamond. After all…the diamond will be held in the setting by the girdle, and, while being worn on the finger by its owner…there is a greater chance that the wearer will bang or knock the stone on its girdle than any other part of the diamond.

The girdle measurement, on a lab grading report, is expressed in either millimeters, or as a percentage of the stone’s total depth. It is important to have a girdle that is the right thickness. The girdle should be thick enough to be secure for setting, and secure against chipping or cracking, however if the girdle is too thick, this will hide “extra weight” in the stone. “Extra weight” is carat weight that you pay for in the price, but don’t see in the actual millimeter diameter of the diamond. There are many places that diamond cutters can hide weight in a stone…the girdle is just one. We will discuss them more in detail later on in this tutorial.

Now that we have taken the time to breakdown the different facets a diamond…we are going to focus on breaking down our next look into the world of cut by considering one shape and cut pattern at a time.  We will continue this discussion in Chapter 5.

Written by Timothy Andre, Emma Parker & Co.     www.emmaparkerdiamonds.com