The Four C's | The 4 C's | Diamond Cut, Color, Clarity & Carat

Before you start looking for a diamond, you want to have all of the necessary information that is available to you, because the more you know, the better prepared you are to make decisions regarding your purchase.

LEARN ABOUT THE FOUR C's

Cut

Color

Clarity

Carat

Diamond Cut

Most diamonds are cut round with a full 58 facets, and a good cut, or make, has more scintillation, more sparkle. It is the work of a master cutter that allows the diamond to be cut in such a way as to permit the maximum amount of light to be reflected through the diamond, and that's a great reflection on you. It is the cut that enables a diamond to make the best use of light.

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COLOR GRADING

The most common diamond color is yellow. Most diamonds have a slight hint of yellow and the diamond color scale is based on the amount of yellow present in a diamond. Diamond color is graded according to the GIA Grading Scale. Grades are based on the amount of yellow that is visible when viewed facedown through the pavilion on a white diamond color card using daylight equivalent fluorescent light. Each color grade is based on a very small range. When a diamond is color graded it is compared using a set of master stones. Master stones are a set of real diamonds that display a range of known colors. It is extremely difficult to see the color differences within diamonds, but master stones help graders distinguish between one color and the next.

As you can see the color-grading scale ranges from D to Z. The highest color grade and whitest stone available is a D color diamond. This is also the rarest color grade, which translates to a higher value. Colors E and F have no detectable color to the naked eye and they fall into the Colorless category. Diamonds in the G to J color range have a hint of body

color and are considered Near Colorless. The eye begins to detect faint traces of yellow in diamonds that are in the J to M range. Diamond Ideals typically sells diamonds in the color range of D to J and occasionally K.

The AGSL uses a slightly different color grading scale. The AGSL ranks the stones from 0-10, in 0.5 increments with 0 representing the equivalent of colorless D stones, and 10 representing the equivalent of X, Y and Z colored diamonds.

Ideal Cut Diamonds Can Mask Subtle Color Differences: Ideal Cut diamonds offer a little flexibility in color selection. Because Ideal Cut diamonds are designed to maximize brilliance and scintillation they also tend to mask subtle color differences making H and I color diamonds appear beautifully white. Ideal Cut H and I color diamonds tend to appear whiter than poorly cut diamonds of the same color.

Color can save you money

A diamond's color grade does not pertain to the "face-up" look of a particular diamond, but rather to the "body" color of the material. The best way to assess diamond color is to view it from the side, un-mounted, against a white background, using a daylight fluorescent bulb.

An AGS Triple Ideal Cut Hearts & Arrows diamond reflects more than 99% of the light back through the crown. There is virtually no light leakage in these stones. What this means to you is that rather than seeing the diamond's color, when you look at a Hearts & Arrows diamond, all you see is white light and scintillation. These diamonds appear whiter than non-Ideal diamonds. Keep this in mind if budget is an issue. By dropping one color grade in an AGS Triple Ideal Cut Hearts & Arrows diamond, you will not be giving up anything in the look of your diamond and you will be saving money.

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CLARITY

The diamond's clarity is a description of its internal purity. With fewer imperfections within the stone, the diamond is more rare and has a higher value. The clarity scale was developed by the Gemological Institute of America (GIA) to quantify these imperfections. The American Gem Society (AGS) uses the same standards as the GIA; however, the AGS uses a numerical system where "0" is the cleanest (GIA "IF") and "10" is the most imperfect (GIA "I3").

All diamonds are systematically graded and plotted under 10X magnification. If a trained grader cannot see a clarity characteristic at 10X, it does not affect the clarity grade.

Five Factors That Determine Clarity

Size Number Position Nature Color

All of the above factors are taken into consideration when a diamond is assigned a clarity grade.

Clarity Grades Defined by the GIA

Flawless — Flawless diamonds have no inclusions or blemishes when viewed under 10X magnification by a skilled grader. A diamond can have naturals confined to the width of the girdle, extra facets on the pavilion that are not visible face-up, laser inscriptions confined to the girdle and internal graining that is not white, colored or reflective.

Internally Flawless (IF) — An IF diamond has no inclusions, only blemishes when viewed under 10X magnification.

Very Very Slightly Included (VVS1 and VVS2) — VVS diamonds contain minute inclusions that are difficult for a skilled grader to see under 10X magnification. The inclusion in a VVS1 diamond are extremely difficult to see face-up, or may be visible only through the pavilion. Inclusions in a VVS2 diamond are very difficult to see. Typically VVS diamonds have a pinpoint or two; however, characteristics like a bearded girdle or tiny chips might also be present in VVS diamonds depending on their visibility.

Very Slightly Included (VS1 and VS2) — Diamonds of VS clarity contain minor inclusions that range from difficult (VS1) to somewhat easy (VS2) to see under 10X magnification. Typical inclusions in VS diamonds include small crystals, feathers and distinct groups of pinpoints.

Slightly Included (SI1 and SI2) — Diamonds of SI clarity contain noticeable inclusions that are easy (SI1) or very easy (SI2) to see under 10X magnification. Typical inclusions, such as crystals, clusters of pinpoints and feathers, are centrally located.

Included (I1, I2, and I3) — Diamonds in the 'I' clarity range contain inclusions that are obvious under 10X magnification. These inclusions can often times be seen face-up without magnification, sometimes affect the stone's durability and can be so numerous or large that they affect transparency and brilliance.

The clarity is typically assigned by a first impression or at first glance. The grader notes whether the inclusions are easy, difficult or very difficult to see when they first look at the stone. The clarity grade of most diamonds is determined in less than 2 minutes. The exception to this is in Internally Flawless and Flawless diamonds, which take considerable examination to assign such a high and valuable grade. It of course takes longer to plot included diamonds as well.

What is Eye-Clean

"Eye-clean" is a term used to describe a diamond or an inclusion that is not visible to the unaided eye when the diamond is held face-up (viewed through the table) at a normal viewing distance of 10 to 12 inches. Nearly all VS clarity diamonds are eye-clean, most SI1 clarity diamonds are eye-clean and some SI2 and even I1 clarity diamonds are eye-clean.

An inclusion is called "eye-visible" when it is visible to the unaided eye, without magnification.

Types of Clarity Characteristics

There are two basic categories of clarity characteristics, inclusions and blemishes.

Inclusions are clarity characteristics that are completely enclosed in a polished gem or those extending into it from the surface. Examples of inclusions are as follows:

Crystal — Another mineral crystal contained in the diamond. These crystals can include other diamonds, garnet or a host of other minerals.

Needle — A long, thin crystal.

Pinpoint — A very tiny crystal that looks like a dot or speck of dust. Pinpoints often congregate in clusters or clouds.

Twinning wisp — A series of pinpoints, clusters or crystals that formed in a twinned diamond's growth plane.

Internal graining — The appearance of faint lines, angles or curves caused by crystal growth.

Feather or gletz — A general term for any break or fracture in a diamond.

Bearded girdle — Minute feathers that extend from the girdle surface into the stone.

Indented Natural — The original crystal surface, or skin, that dips below the polished diamond's surface.

Knot — An included diamond crystal that extends to the surface after polishing.

Cavity — Space left when a surface-reaching crystal comes out during polishing.

Blemishes are external clarity characteristics caused by wear, the cutting process or the diamonds crystal structure. Examples of blemishes are as follows:

Nick — A small chip-like characteristic.

Abrasion — A series of minute nicks along a facet junction.

Scratch — A thin, dull, white line across the diamond's surface.

Natural — A portion of the original skin that remains on the diamond.

Pit — Small surface characteristic that looks like a tiny dot.

A Note on Clarity Enhancement

Diamond Ideals does not sell any clarity-enhanced diamonds.

Clarity enhancement is a treatment to improve a diamond's apparent clarity. A diamond with eye-visible inclusions can be seen as less desirable. To make the diamond more desirable and marketable, some sales people have the diamond clarity enhanced to make the eye-visible inclusions less visible or invisible to the naked eye.

There are two common types of clarity enhancement. The first type of clarity enhancement is called laser drilling. Laser drilling is the use of a laser to drill a small hole in the diamond, extending to reach a visible inclusion such as a black crystal. Sometimes an acid is used to bleach or dissolve the included color, improving its appearance. Laser drill holes can typically be seen as tube like inclusions in the diamond when viewed perpendicular to the point of entry under 10X magnification. The hole can also be seen as a tiny pit-like blemish on the surface, under reflective light of a microscope.

The second type of clarity enhancement is fracture filling. Fracture filling involves the use of a molten glass substance to fill or mask the reflective qualities of an internal fracture. Fracture filling can be detected by the telltale 'flash effect' that the filling produced. The flash effect can be seen as two distinctly different colors that appear when you rock and tilt the diamond in different directions. Some untreated feathers can show an iridescent rainbow of colors from all directions, so it is important to know the differences.

Fracture filling is not a permanent treatment and therefore GIA does not grade fracture filled diamonds. GIA does, however, grade the permanent laser drilled diamonds.

Again, Diamond Ideals does not sell any clarity-enhanced diamonds.

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Carat Weight

A carat is a weight measuring unit equal to 0.2 grams. It is the internationally used unit to measure the weight of diamonds. Within the diamond trade, fractions of a carat are referred to as "points" or simply as fractions. A 50-point diamond weighs 0.5 carats or 1/2 a carat. A 1-carat diamond weighs 100 points. A 1/3 is also 0.3 carats or 30 points.

As nature would have it, rough diamonds come in all shapes and sizes, as well as colors and purities. The larger, whiter and cleaner the diamond, the more rare it is. Accordingly, the cost per carat of a larger diamond of the same color, clarity and cut will be higher than a smaller diamond. The price per carat of diamonds rises proportionately with size. Keep in mind that the per carat price gets multiplied by the carat weight.

More weight equals more money so, many diamond cutters sacrifice brilliance to maximize carat weight and profit. It is important to realize that weight does not always equal size or beauty. Poorly cut diamonds intended to maximize size can be dull and lifeless. Some experienced cutters sacrifice weight and focus on cut to obtain the most beautiful and brilliant Hearts and Arrows diamonds on the market today. On the average, cutting a Hearts and Arrows Ideal Cut Diamond requires a 15% greater waste of the original material. The added beauty one obtains from a Hearts and Arrows diamond is well worth the sacrifice. Diamond Ideals specializes in sourcing these cutters and bringing the most beautiful diamonds to you.

The following is a chart indicating the average mm size per carat:

DiamondIdeals’CutGrade

At the request and suggestion of many of our customers, we have developed a Cut Grade system to be used as an initial sorting tool. As we have always insisted, the determining factor for any stone will be the eyes of a diamond professional and ultimately you. This is especially true when it come to fancy shaped diamonds. The American Gem Society Laboratory (AGS) has developed cutting standards for round and princess cut diamonds and the Gemological Institute of America (GIA) had developed standards for rounds as well, but there are no standards for cushions, asschers, emeralds, ovals, etc… The Cut Grade determinations we have developed do not take overall shape into consideration. Each stone must be reviewed by our in-house gemologists as we work with you. We often make side by side comparisons to help you make an informed and confident decision.

Our Cut Grade is determined using a combination of factors including polish, symmetry, table %, depth % and how these proportionately relate to each other. This is intended as an initial sorting tool, not an absolute stamp of approval or disapproval for any particular stone.

A diamond’s individual measurements (table, depth, crown angles, etc…) can be within the most desired range, however, it is how these attributes relate to each other that ultimately determines how much light entering the diamond is going to be reflected back out through it’s table. This is what is referred to as “performance”. Both the GIA and the AGS laboratories have made performance the cornerstone of their new cut grade. Two stones with very similar numbers can look very different: one can be full of sparkle and fire while the other can look rather dull.

Over the years, as we have scanned lists of thousands of stones, we have developed a method to quickly assess which stones will be poor performers, which are most likely to be exceptional and all those in between. Prices of these diamonds, more often than not, reflect the cut quality or Cut Grade. Two stones of similar weight, color and clarity will have very different appearances and prices depending on their over-all cut quality. The Cut Grade system we have developed is an excellent initial sorting tool. As opposed to many on-line diamond stores who drop-ship stones directly from the wholesaler to their customer without ever seeing the diamond, we carefully inspect each and every diamond as we work with our customers. Our goal is for you to purchase the perfect diamond for you.

We have created five Cut Grades:

Elite Ideal Cut Grade is reserved for those exemplary diamonds which have met our strictest quality control standards. Each and every one of these diamonds has been hand picked and is absolutely stunning. These diamonds have been graded by the AGS Laboratory as being Ideal in polish, symmetry, proportion and light performance. Elite Ideal Cut stones exhibit a perfect Hearts & Arrows pattern and are accompanied by a Gemex BrillianceScope report attesting to their extraordinary light performance (stones 0.7cts and larger only). As an added benefit, our Elite Ideal Cut diamonds are laser inscribed for your protection and assurance and come with a Lifetime Upgrade Policy.

Our Elite Ideal Cut inventory is in-house and all of the images and reports are immediately available through our “Miner Report”. Just click on "Miner Report" next to the listed price of each stone, submit your name and email address and the information will be sent to your inbox within a few moments.

   

Excellent Cut Grade has been determined based on parameters found on grading reports. In our initial survey of these stones we believe the combination of factors listed on these grading reports offers the highest potential for excellent fire, scintillation and brilliance. The proportions of these diamonds are such as to maximize the look of the stone without sacrificing their sparkle or performance. Even considering the initial read of the grading report, we still strongly suggest having our gemologists assess these diamonds.

Very Good Cut Grade has been determined based on parameters found on grading reports. In our initial survey of these stones, we believe the combination of factors listed on their grading reports offer an excellent value of cut and price. These diamonds are more than likely have average sparkle and performance, but their price can be very attractive. We still strongly suggest having our gemologists assess these diamonds.

Good Cut Grade has been determined based on parameters found on grading reports. In our initial survey of these stones, we believe the combination of factors listed on their grading report offer an excellent value. These diamonds may not have the sparkle seen in better cut stones, but their price can be very attractive. We strongly suggest having our gemologists assess these diamonds.

Fair Cut Grade has been determined based on parameters found on grading reports. In our initial survey of these stones, we believe the combination of factors listed on the grading report is less than optimal. These diamonds may not be well cut stones and we would normally guide you away from them. Their price however can be very attractive. If you are considering purchasing a stone solely based on price, we strongly suggest having our gemologists assess the diamond and make you aware of any potential problems.

DIAMOND ANATOMY

The basic parts of a cut diamond

Verena Pagel-Theisen, Diamond Grading ABC: Handbook for Diamond Grading, 1980, p.154

Table: The flat facet on the top of the diamond. It is the largest facet on a cut diamond.

Crown: The upper part of the diamond above the girdle. Consists of a large flat area on top called a table, and several facets below it

Girdle: The outer edge or the widest part of the diamond forming a band around the stone.

Pavilion: The bottom part of the Diamond, below the girdle.

Culet: A tiny flat facet that diamond cutters sometimes add at the bottom of a diamond's pavilion. Its purpose is to protect the tip of the pavilion from being chipped or damaged. Once a diamond is set in jewelry, though, the setting itself generally provides the pavilion with sufficient protection from impact or wear. Large or extremely large culets were common in diamonds cut in the early part of this century, such as the Old European or Old Mine Cut. However, such large culets are rarely seen today. Most modern shapes have either no culet at all, or a small or very small culet.

Depth: The height of a diamond from the culet to the table. The depth is measured in millimeters.

Crown angle: The angle at which a diamond's bezel facets intersect the girdle plane. This gentle slope of the facets that surround the table is what helps to create the dispersion, or fire, in a diamond. White light entering at the different angles in broken up into its spectral hues, creating a beautiful play of color inside the diamond. The crown angle also helps to enhance the brilliance of a diamond.

Table percentage: The value which represents how the diameter of the table facet compares to the diameter of the entire diamond. So, a diamond with a 60% table has a table which is 60% as wide as the diamond's outline. For a round diamond, gemologists calculate table percentage by dividing the diameter of the table, which is measured in millimeters (this millimeter measurement does not appear on diamond grading reports) by the average girdle diameter. For a fancy shape diamond, table percentage is calculated by dividing the width of the table, at the widest part of the diamond, by the millimeter width of the entire stone.

Facet: The smooth, flat faces on the surface of a diamond. They allow light to both enter a diamond and reflect off its surface at different angles, creating the wonderful play of color and light for which diamonds are famous. The table below shows all the facets on a round brilliant cut diamond. A round brilliant has 58 facets (or 57 if there is no culet).

Symmetry: Refers to variations in a diamond's symmetry. The small variations can include misalignment of facets or facets that fail to point correctly to the girdle. Symmetry is regarded as an indicator of the quality of as diamond's cut; it is graded as either Ideal, Excellent, Very Good, Good, Fair or Poor.

Fluorescence: An effect that is seen in some gem-quality diamonds when they are exposed to long-wave ultraviolet light (such as the lighting frequently seen in night clubs). Under most lighting conditions, this fluorescence is not detectable to the eye. However, if a diamond is naturally fluorescent, it will emit a soft colored glow when held under an ultraviolet lamp or "black light." Fluorescence is not dangerous to the diamond or to the wearer; it is a unique and fascinating quality that occurs naturally in a number of gems and minerals. Most commonly diamonds fluoresce blue, but can also fluoresce yellow or white depending on which trace elements are found in the matrix of the diamond crystal. Fluorescence is described as none (or inert), faint, negligible, medium, strong and very strong.

Fluorescence in diamonds can have both favorable and undesirable effects. For example, diamonds in the color range of I to N with medium to strong blue fluorescence can appear more colorless, which is an obvious advantage. The blue acts to mask or offset the very faint

body color of these diamonds. On the other hand, diamonds with very strong fluorescence can exhibit an oily or milky appearance, even under incandescent lighting. However, according to a GIA study, the average observer could not detect any difference in color or transparency when viewing diamonds with fluorescence.

WHAT MAKES A DIAMOND SPARKLE

Brilliance is an essential attribute of a beautiful diamond and has 2 components; brightness and contrast. Bright diamonds return lots of light from the surroundings back to a 'face up' an observer. If light from above leaks out the back of a diamond, naturally it has less brightness. But light that enters and leaves in the face up direction is wasted because your head blocks the lights. Diamonds that are too deep or very shallow do this -they have areas that act like a mirror back to the viewer; they return less light and so they have less brightness.

To be brilliant, a diamond needs more than just brightness. Consider the contrast of a chess board, although it has only 1/2 the light return of a sheet of white paper, it appears brighter, especially when it is moved because it 'scintillates'.

Fire or dispersed light appears as flashes of rainbow colors. You see more fire in darker environments like restaurants that have just a few point light sources or just a flickering candle. Fire is also a result of a diamond's symmetry and proportions. There are several factors that greatly influence the amount of fire a diamond produces such as star facet length, lower girdle facet length, pavilion angle, facet junctions, the angle at which light enters the diamond, and the angle of the light rays as they exit the diamond.

Diamond experts have known for a long time that steep crown angles and small tables (like 'old cut' diamonds) produce more fire. But this combination also produces less light return. Less light return makes it easier to see fiery flashes that might otherwise be swamped by bright white sparkles; that one reason is why old cut diamonds and some fancy cuts appear to have a lot of fire.

Scintillation is the intense sparkles in a diamond as it moves. Black and white sparkles of scintillation show well in flood lit or office lighting environments where fire can be totally absent. Under pin point or spot lights fire also adds to scintillation. Ideally a diamond has many pleasing flashes spread across the surface of the stone, with few dull dead patches.

Polish is graded the same way as symmetry: Ideal, Excellent, Very Good, Good, Fair or Poor on a GIA report. Poorly polished facets may reduce the intensity of light reflected from, or refracted into and out of, a diamond. Labs assess polish by examining the diamond, facet by facet, with reflected light under a microscope; you or I may not see any difference.

How symmetry and proportions maximize light return

Every facet in an AGS Ideal Cut diamond must be placed at precise angles and contain precise proportions. This ensures an Ideal balance between maximum brilliance and dispersion of light. Any discrepancy from these proportions will disrupt the even distribution and dispersion of light within the stone, resulting in a loss of sparkle.

A well-proportioned pavilion is especially important to a diamond's brilliance. Brilliance is the brightness created by the combination of all the white light reflections from the surface and the inside of a polished diamond. If the pavilion is too deep or too shallow, it causes light to strike outside the critical angle - the largest angle at which light rays inside the diamond can escape - causing the light to exit through the pavilion rather than reflecting back to the eye as brilliance.

EVALUATION & GRADING TOOLS

Hearts and Arrows Viewer

Hearts and Arrows is a visual phenomenon that appears in the finest Ideal Cut round brilliant diamonds when viewed in a Hearts and Arrows viewer or gemscope. Diamonds cut with precisely aligned and carefully shaped facets combined with optimum proportions produce an incredibly brilliant sight, called Hearts and Arrows.

The viewer is merciless when it comes to any deviation from perfection. Any detour from the correct path of light will result in the deformation or absence of either the hearts or the arrows. This device, as unassuming as it may appear can clearly show even the untrained eye how well or how poorly a diamond is cut.

Diamond Ideals will give you (FOR FREE) a Hearts and Arrows viewer with every purchase of a diamond larger than 0.5 carats.

OGI Megascope

The OGI Megascope is a high-tech, Electro-optical device used to analyze the cut parameters of precious stones. The software associated with this high-tech device makes several types of

analyzing functions available. The technology has the capability of analyzing each and every facet as well as the diamond's diameter, crown angle and height, pavilion angle and depth, culet size, culet placement, table size, table placement, table depth, girdle thickness and other relevant characteristics.

The purpose is not only to confirm a diamond's cut grade, but also to allow you to expand on the cut information provided in the AGS report and numerically visualize the precise symmetry of our Hearts and Arrows diamonds.

Please note, this analytical device has a measurement accuracy of 0.2° for the crown and pavilion angle, 0.3% for the table and 0.015 mm for the diameter. Therefore, results may vary slightly from the AGS certificate. We consider the AGS certificate to be the authority when analyzing proportions though similar Sarin technologies used by the AGS have their own tolerances.

IdealScope

The IdealScope is a device that helps grade the cut quality and performance of diamonds. This little device shows you areas of light leakage in diamonds you are considering for purchase. Light leakage can be seen as areas of pure white within and around the diamond. It is important to note that all diamonds have some leakage, particularly under the table and around the diamond's edge. This minor leakage is seen as pale red areas or small white wedges near the edge of the diamond. What is important is to notice the presence or absence of large white spots in the IdealScope image. Large white areas are an indication of significant light leakage.

The pictures are not taken with scientific accuracy but are set up manually, leaving room for small optical inconsistencies.

Below is an IdealScope chart depicting the difference between excellent and poor performing diamonds.

This is what our diamonds typically look like through an IdealScope. Nearly all of our diamonds fall in the excellent to very good range.

Chart created by Ideal-scope.com

BrillianceScope

The BrillianceScope is a device that provides a comparative light performance evaluation of diamonds. Measuring the play of light in a diamond to determine its light performance from 6 different positions, the BrillianceScope analysis gives you an idea of how a particular diamond will perform in direct light conditions.

The analysis is based on a scale that compares three components of light performance to standards established for diamonds with the same shape. The result is a measurement of the

percentage of the diamond returning various types of light. Note this is different from the percentage of light being returned to the observer.

Light Performance

Light performance takes into consideration three types of light return: white light, color light and scintillation.

The BrillianceScope measures the percentage of the diamond returning bright white light to the observer. Essentially this shows you how much of the diamond and what parts of the diamond exhibit brilliance.

Fire is another type of light return measured by the BrillianceScope and is determined by the percentage of the diamond returning bright color light to the observer.

The BrillianceScope also measures scintillation — the flashes of light you see when the diamond, the light, or the observer moves. The analysis measures the number of light points and determines how they change from position to position.

GRADING REPORTS & INSCRIPTIONS

The American Gem Society (AGS) Laboratory was the first and foremost independent laboratory to issue numerical cut grades. Originally, this grade was based primarily on proportions measured on a Sarin Diamension machine. The AGSL now incorporates the performance of the diamond in its analysis. The highest grade is "0 Ideal." As a stone deviates from perfection, its numerical grade increases; 1 Excellent, 2 Very Good, all the way down to 10 Poor. As technology has improved, so has the grading.

The AGS grades eight aspects of cut of each stone it analyses. These include the Crown & Pavilion Angle, Pavilion Depth, Table Diameter, Girdle Thickness, Culet Size, Polish, Symmetry and Performance. The first five of these are grouped under the term "Proportion."

The AGS gives its highest cut grade to a stone that has achieved the highest (actually lowest "0") score on all four criteria: Polish, Symmetry, Proportion and Performance. Remember that not all AGS Triple Ideal Cuts achieve the more precise demands of Hearts & Arrows.

AGS Lab Diamond Quality Document

GIA Grading Reports - The GIA is the most recognized grading lab in the world. A few years ago, the GIA finally started providing a cut quality.

The GIA and AGS labs are the most consistent in their grading and abide by the highest standards. The primary difference between these two labs has to do with popularity. The AGS developed an early loyal following primarily of manufacturers specializing in the highest cutting standards. The GIA is better known as their grading reports did not mention cut quality until recently. Today's economy is a global market and the choice of one lab over the other will primarily depend on where the manufacturer of any given stone does the most business.

EGL Grading Reports - Why are EGL graded diamonds so much cheaper than AGS or GIA graded stones?

The simple answer is that gemological labs are not all held to the same grading standards. The EGL is more lenient in their grading than the GIA and AGS. Color differences can be as much as 3 to 5 color grades and clarity grades are typically 1 to 2 grades lower than GIA and AGS standards. As such EGL graded diamonds are priced lower.

For the purpose of this section, we will consider the AGS and GIA as equal in their standards of grading.

In the words of a very wise diamantaire: "The GIA is a tool for buying diamonds. The EGL is a tool for selling diamonds." That in a nutshell is the difference. The European Gem Lab does not have the same strict grading standards as do the GIA and AGS, thus they tend to be more

lenient and inconsistent in their grading assessments. Simply put, this means that a diamond graded by the EGL would more than likely be graded lower by the GIA. Unfortunately this means that if you are comparing an EGL F-SI1 and a GIA F-SI1 of the same carat weight you will not be comparing apples to apples and you should expect the EGL graded stone to cost less than the GIA stone. We have seen differences as great as 5 full color and/or 2 clarity grades between the labs. The price is reflective of the leniency of the grading.

For example:

GIA Round 1.51 F-SI1 Excellent Cut for $15,845

AGS Round 1.54 F-SI1 Ideal Cut for $16,160

EGL Round 1.51 F-SI1 Excellent Cut for $8,803

That is nearly a 50% difference (lower) price for the EGL graded diamond. Considering that you always get what you pay for, a safe assumption about this particular EGL diamond is that it is at 3 to 5 color grades and one or two clarity grades lower, by GIA standards. We should really read this stone as an I/J-SI2/I1 diamond by GIA standards. Looking at equivalent grades in the other labs we see that this really is no bargain:

EGL Round 1.51 F-SI1 (really I/J-SI2/I1) Excellent Cut for $8,803

GIA Round 1.50 J-SI2 Excellent Cut for $8,761

The above diamonds and prices are examples taken from our inventory in March 2012 for comparison and illustration only. These specific diamonds may not be available for sale.

Laser Inscription

A laser inscription is a name or number that is burned into the diamond girdle to help identify it. The inscription is like an engraving that is not just on the surface but is etched or burned fractions of a millimeter into the diamond. Diamonds are laser inscribed when the manufacturer send his stones for certification. Laser inscriptions are done by the grading labs and are mentioned on the grading reports in the "Comments" section. As this process adds significantly to the cost of the grading report, some manufacturers chose not to have their stones inscribed. If a diamond does not have a laser inscription, you can easily use the inclusion plot on the grading report to identify your stone. Every diamond has a unique arrangement of inclusions that can serve as a fingerprint.

Most Elite Ideal Cut diamonds at Diamond Ideals have their report number laser inscribed in the girdle. This adds a degree of security, which can be useful in case you ever need to have your jewelry cleaned or repaired.

The black that you see in the laser inscription is actually burnt carbon residual left over from the laser burning. After the diamond is mounted, the jewelry cleaning process involves ultrasonic and steam cleaning, which may remove this carbon residual, making the inscription appear white or clear. This does not change the fact that the stone is laser-inscribed. While it may become more difficult to see under a loupe, the inscription on your diamond will still be visible when viewed under a microscope.

Here are a couple of magnified images depicting the visibility of the laser inscription before and after the carbon residue has been removed from cleaning.

 

 

 

 

 

 

 

MANUFACTURING THE DIAMOND

Cut is the only diamond characteristic under human control, and considered by many to be the most important. A good cut can offset a lower color or clarity; however, even a D-color, Internally Flawless stone will not look its best if the cut or "make" is poor. A poor cut actually reduces the brilliance, sparkle and scintillations of a diamond.

MORE INFORMATION

Cutting Process

Four Basic Steps For Diamond Cutting

The decision to cut a diamond in a particular shape is dictated by the natural shape of the rough stone. Some stones are naturally oblong and are destined to become marquises, ovals or pear shapes. Some rough diamonds occur in near perfect crystal shapes and these will more than likely be cut as princess cuts or some other square cut.

Diamond cutting is a lengthy and difficult task, requiring a great deal of knowledge and experience. Understanding this process may give you some appreciation of the various aspects of creating your gorgeous Diamond Ideals diamond.

CUTTING PROCESS

Diamond cutting has been a work in progress since the first diamonds were cut in the mid 1300s. Cuts have evolved from the first and most simplistic point cut - a basic four-sided cut that resembles the outline of rough octahedral crystals - to the table cut, single cut, old mine cut, old European cut and finally the modern brilliant cut. When the single cut was developed in the early 1600s it became apparent that more facets meant more brilliance and it was the single cut that laid the foundation for the modern brilliant cut that is so popular today.

The modern round brilliant cut diamond consists of a round outline, symmetrical triangular and kite-shaped facets, a table, and a small culet or no culet at all.

Verena Pagel-Theisen, Diamond Grading ABC: Handbook for Diamond Grading, 1980, p.154

Incredible amounts of patience, skill and consideration are required to transform the world's hardest material into a beautiful and valuable polished gem. A cutter must carefully consider the size, shape, cleavage planes and even inclusions when preparing to fashion a rough diamond. The ultimate goal is to end up with the best cut and the most carat weight possible at the lowest production cost. This results in some difficult decisions.

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THE FOUR BASIC STEPS FOR DIAMOND CUTTING

Planning

Planning is a crucial step in diamond manufacturing because during this stage the size and relative value of the cut stones that the rough will produce are determined. A person called a planner decides where to mark the diamond rough for fashioning into the most profitable polished gem(s). The planner must consider the size, clarity and crystal direction

when deciding where to mark the diamond rough. Incorrectly marking a diamond by a fraction of a millimeter can make a difference of thousands of dollars in some cases. In addition, if one attempts to cleave a diamond in the wrong position, the diamond could shatter and become worthless.

Cleaving or sawing

Once the planner decides where the diamond should be cut, the diamond is either manually cleaved or sawed. Sawing can be done with a diamond-coated rotary saw or a laser.

Bruting

Bruting forms the basic face-up outline of a round diamond to prepare it for faceting. During the bruting phase the diamond being bruted is spun on a rotating lathe while another diamond is forced against it, gradually forming the rounded outline. Essentially, one diamond is used to shape the other.

Polishing

Polishing is the final stage of the cutting process, giving the diamond its finished proportions. The first and perhaps most crucial polishing stage is blocking. This step lays the foundation for the potential of the diamond's performance because it establishes the diamond's basic symmetry. During the blocking stage, the first 17 or 18 facets are made, creating a single cut. For some very small diamonds, the process stops here. Larger diamonds go on to the brillianteering stage. In this process a specialist called a brillianteer, polishes the final facets. It is this stage that will determine how much brilliance and fire a diamond displays. Minor inconsistencies in symmetry and proportions can make the difference between a gorgeous diamond and a dull, lifeless stone. The Hearts and Arrows in our beautiful diamonds are the result of a skilled and mastered brillianteer.

 

 

DIAMOND GLOSSARY

BRILLIANCE: The intensity of white light reflected through the top of the diamond.

CROWN: The top part of a diamond, from the girdle to the table.

CULET: The bottom facet at the tip of the diamond.

DEPTH: The height of a gemstone, from the culet to the table.

DIAMETER: The width of the diamond, measured around the girdle.

DISPERSION: The result of white light splitting into all the colors of the rainbow.

EYE CLEAN: A term meaning no flaws are visible to the unaided eye when viewed from 12 inches away, with the diamond face up.

FACE UP: The diamond viewed from the top of the stone.

FACET: The flat, polished surfaces on the diamond. All Diamond Ideals diamonds have 57 facets.

FIRE: When moved, these are flashes of color reflected from within a diamond, resulting from dispersion. Just like a prism, white light entering a diamond separates into all the colors of the rainbow.

FLAW: Any external or internal imperfection in a diamond.

FLUORESCENCE: The luminescence exhibited in certain diamonds when exposed to ultraviolet light or strong sunlight. Fluorescence is most commonly blue in color, but can also be a variety of other colors.

GIRDLE: The narrow band encircling the widest part of a diamond. It may be faceted or non-faceted. All Diamond Ideals diamonds have the AGS certificate number laser inscribed on the girdle for your protection.

INCLUSION: An impurity within a diamond. Inclusions may or may not be visible with the unaided eye. Fewer inclusions ensure a finer clarity grade.

PAVILION: The bottom part of a diamond, from below the girdle to the tip of the culet.

POLISH: The smooth, shiny finish on the facets of a diamond. Ideal polish is critical for maximum diamond brilliance. Diamond Ideals sells only diamonds with Ideal polish, the highest grade given by AGS Labs.

PROPORTIONS: The cutting quality relative to the depth percentage, table percentage, girdle percentage, symmetry and crown and pavilion angle. Proportions influence light refraction and reflection within the diamond. Diamond Ideals sells only diamonds with Ideal proportions, the highest grade given by AGS Labs.

SCINTILLATION: Flashes of reflected light from a diamond when it moves. Commonly referred to as sparkle.

SYMMETRY: The overall uniformity of a stone's cut, which can range from poor to Ideal. The symmetrical alignment of facets makes for a more stunning diamond. Diamond Ideals sells only diamonds with Ideal symmetry, the highest grade given by AGS Labs.

TABLE: The largest, flat facet on the top of a diamond.

 

Color

While many diamonds appear colorless, or white, they may actually have subtle yellow or brown tones that can be detected when comparing diamonds side by side.

Colorless diamonds are the rarest and most valuable of all. Color variations are a result of the natural forces (i.e., temperature, pressure, trace elements) at work during the formation of diamonds within the Earth. Because subtle color variations dramatically affect the value of a diamond, a color grading scale is used to categorize the shading differences from one diamond to the next.

Diamonds are graded according to the GIA (Gemological Institute of America) color chart.

GIA color grade

Description Appearance

D Colorless Stone looks absolutely clear, with no hint of color to the eye in color grading or mounted E

F

G Near Colorless Some color tint is visible during grading. Mounted in a setting, stone appears colorless. GHI color diamonds are considered very nice diamonds for fine jewelry.

H

I

J

K Faint yellow Yellow or grayish tint is obvious during color grading. Mounted, this stone still shows a tint of color L

M

N-Z Light yellow Obvious yellow or grayish color

Z+ Fancy Bright, remarkable color - usually blue, pink, yellow

Clarity is an indication of a diamond's purity. Clarity is determined by a diamond's naturally occurring internal characteristics. These characteristics are sometimes not visible to the naked eye and they are what make each diamond unique. The characteristics, or inclusions, may look like crystals, feathers, clouds or dark spots and the quantity, size, and location of these inclusions does have an affect on a diamond's value. Diamonds with fewer and smaller inclusions generally are more brilliant, assuming that the color and cut are the same.

The U.S. Federal Trade Commission has established the jewelry industry's standards for diamond clarity based on 10-power magnification. A diamond is graded by its relative departure from "flawless"--the complete absence of inclusions under 10x magnification.

Less than 1% of all diamonds ever found have had no inclusions and can be called flawless (FL) or internally flawless (IF). VVS diamonds are also extremely rare. VS diamonds are of superior quality and are used in extremely fine jewelry. This clarity grade becomes more important as the diamond size increases. A large percentage of jewelry is made with SI quality diamonds. These diamonds are perfect for diamond studs or multi-stone diamond earrings, rings and bracelets or as accents in gemstone rings. I quality diamonds are acceptable as well for diamond jewelry or as accents but the sparkle is reduced by the number and location of inclusions.

Clarity Grade

Description Appearance

F Flawless Clear stone, free of all flaws, even under 10x magnification

IF Internally Flawless No inclusions visible at 10x magnification

VVS1 Very Very Slight Inclusion #1

Tiny inclusions are extremely difficult to find, even under 10x magnification

VVS2 Very Very Slight Inclusion #2

Tiny inclusions are very difficult to find, even under 10x magnification

VS1 Very Slight Inclusion #1 Minor inclusions are difficult to see under 10 x magnification

VS2 Very Slight Inclusion #2 Minor inclusions are somewhat difficult to find under 10x magnification

SI1 Slight Inclusion #1 Inclusions are easy to see under 10x magnification. These diamonds are considered "eye clean" since inclusions can not been seen with the naked eye. In larger diamonds very very small inclusions may be visible and still be classified as SI1.

SI2 Slight Inclusion #2 Inclusions and/or blemishes are easy to see at 10x. These diamonds are considered "eye clean" since inclusions can not been seen with the naked eye. In larger diamonds very small inclusions may be visible and still be classified as SI2.

I1 Included #1 Inclusions and/or blemishes are obvious and rather

Carat

Diamonds are measured in terms of weight, not size. The heavier the diamond, the greater the carat weight. Two diamonds of equal weight can have very different values, because the quality is still determined by the color, clarity and cut. As diamonds increase in size, their cost tends to increase exponentially rather than arithmetically. Thus, a one-carat diamond can cost significantly more than a one-half carat diamond of equal quality. The weight of a diamond less than one carat in size may also be described in terms of "points". There are 100 "points" in 1 carat.

Carat Weight Diameter

0.03 carats 2 mm

0.10 carats 3 mm

0.25 carats 4 mm

0.45 carats 5 mm

0.50 carats 5.2 mm

0.80 carats 6 mm

1.25 carats 7 mm

DiamondValue‐The4C's

Diamond Value - The 4Cs

easy to see without magnification.

I2 Included #2 Inclusions and/or blemishes are obvious and easy to see without magnification

I3 Included #3 Inclusions and blemishes that are obvious to the unaided eye

 

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Learn to evaluate the value of a gemstone 

Buying a colored gemstone, does not have to be an uncomfortable experience. The GemsFeed 4 C's Guide along with the Buying Guide are designed to give you the tools and information you need to properly evaluate a gemstone quality and value with confidence.

Determining the value of a gemstone, just like a diamond, is crucial before you purchase a stone that you will set in a jewelry or that you will resell at profit. The more you understand about what affects the price of a natural gem, the more you will be able to get value for your money.

The4C's‐Carat,Color,Clarity,CutEvery gem is unique, and there are many factors which affect their price, such as the weight and size of the

gemstone (carat), the intensity and tones (color), the presence of internal inclusions (clarity) and the proportions

and luster (cut). Focus on those factors most important to you, and choose a natural gemstone that satisfies your

individual standards for beauty and value.

There is no particular order of importance in the 4 C's. For example if you prefer the size over the color, you

could chose a 2 carats ruby of weak color for the same price as a 1 carat pigeon blood ruby. It is all about

personal preference, but always remeber that the 4 c's are all important. A top color saphir of 10 carats that is

heavily included will be worth very little. In color stone the factor that is often forgotten is the cut, so make sure

you also read that section. At GemsFeed, we want to help find the best gemstone for you. You can also read our

Buying Guide to get a good understanding of each variteties.

Jump to CARAT, COLOR, CLARITY, CUT.

Carat

Gemstones, just like diamonds, are sold by the carat (shown as ct), which is a unit of weight, though many think of a carat in terms of size. The word "carat" comes from the "carob" seed, the original unit of measure for gem traders. Today, a carat is equal to exactly 0.2 grams (about the weight of a paper clip). Carat weight is unrelated to the similar sounding karat, which refers to gold's purity.

As the carat size of a gemstone increases, the gem's price increases at an exponential rate. Why? Because the larger the gemstone, the more increasingly rare it is. For example, fewer than one in one million mined rough rubies are large enough to produce a finished 1 carat ruby. So, as carat weight increases, you will typically pay more not only in total, but on a price-per-carat basis as well. The table below illustrates the typical relationship between gemstones of equal quality and increasing carat weights for rare and valuable gemstones such as tsavorites, saphir, ruby, emerald, diamond, spinel, etc. But for some other stones such as amethyst, citrine, zircons, the prices per carat do not increase much with the weight.

Lets take for example a top quality pigeon blood burmese ruby:

Carat Weight  1.00  2.00  3.00

Price Per Carat  $5,000 $10,000  $20,000

Total Price  $5,000 $20,000  $60,000

The price for a 3 carats ruby is much more than 3 times the price of a similar quality 1 carat ruby because of the exponential value of price per carat.

Now lets take for example a cambodian blue zircon of deep blue color:

Carat Weight  5.00 10.00  20.00

Price Per Carat  $100 $200  $400

Total Price  $500 $2,000  $8,000

As you can see the price of the stone increases with the weight but not as much as the previous example, because zircons are more easily found in larger sizes than rubies. Other factors also determine the price per carat for each gemstone, such as the market demand. Make sure you read our buying guide on each variety of gemstone.

Color

While there is no standardized system for judging the color of gemstones, many jewelers consider it to be the most important criterion for evaluating gemstones. Color that is vivid, even and saturated throughout the entire stone makes a gem more valuable.

Changes in the lighting environment will cause visual changes in the colour of gemstones, thus stones are graded whilst held by their girdle, face up, against a neutrally coloured background and at a distance of approximately 10 inches under a diffused and daylight-equivalent light source, and at a distance of about 18 inches from the viewer’s eyes. Some gemstones will ‘bleed’ colour i.e. loose their colour if the lighting environment is changed from daylight to incandescent light, and others may ‘colour change’.

When describing gemstone color, jewelers speak in terms of three characteristics: hue, saturation and tone.

Hue refers to a gemstone's basic color. The human eye can discern approximately 150 different hues; however, only 31 are widely utilized in gemmology and serve for the vast majority of gemstones. Those gemstones with purer hues are generally considered more valuable; for example, green for tsavorites, blue for sapphires and red for rubies. Sometimes there is a hint of another color. Tsavorites may range from yellowish green to bluish green, sapphires from purplish blue to greenish blue and rubies from orangey red to purplish red.

Hue is defined as the position of the colour on the colour wheel, or the spectral location of a given sensation of colour.

GIA 31 basic gem hues

Saturation is a measure of the color’s intensity or purity. It is determined by the degree to which the stone is free from muting gray or brown hues. The most desirable gemstones, with saturation described as "vivid" or "strong," show little gray or brown. Since value increases with saturation, a fully saturated bluish green emerald may very well be more expensive than a muted pure green one.

Generally speaking cool colours are modified in shades of grey and warm colours are modified in shades of brown.

Tone represents the depth of color and is a measurement of the color’s lightness or darkness, ranging from colorless to black. Jewelers describe tone as either light, medium-light, medium, medium-dark or dark.

Tone measures in an 11 step scale. If a gemstone is too light in tone it will not have a rich colour, and likewise, if a gemstone is too dark, it will compromise brilliance and transparency. The best colours have a tonal range of 50% to 70%; however, gemstones also have different optimal tone and saturation values based on the colour produced in nature.

1.Colourless/white 2.Extremely ligh 3.Very light 4.Light 5.Medium light 6.Medium 7.Medium dark 8.Dark 9.Very dark 10.Extremely dark 11.Black

Clarity

Each gemstone is comprised of a unique combination of trace minerals. These create tiny fractures or mineral flaws called “inclusions.” Under magnification or by their careful unaided eye, gemologists take note of inclusions as well as “blemishes” or surface irregularities in gems. GemsFeed Clarity grades range from IF (Internally flawless) to I (Included).

As with diamonds, the type and location of inclusions are more important than the fact that inclusions exist in the gemstone. It is important that any inclusions do not penetrate too deeply into the stone, because this may affect the gem’s durability, causing it to crack or break. Deeper colors can mask imperfections better, so it is more important in lighter colored stones to select those with fewer blemishes or inclusions.

Flawlessness in gemstones is even more rare than in diamonds. Gemstones with few or no inclusions are available, but they are usually much more expensive. Even most high-end gemstones are at least slightly included. Being more common, sapphires in jewelry tend to have higher clarity levels than rubies. Internally flawless sapphires are very rare, but internally flawless rubies are extremely rare. When considering a colored gemstone's clarity, you should measure your expectations against the standard for that variety of gemstone. Some varieties of colored gemstones, such as aquamarine, blue topaz, and citrine, have naturally fewer inclusions while other gemstones, such as emerald and ruby, tend to have a higher rate of acceptable inclusions.

Below is a chart that explains how GemsFeed grade the clarity of each gemstones.

Cut

There is no generally accepted grading system for gemstone cut. However, like diamonds, a gemstone's cut refers to its proportions and symmetry. Valuable colored gems will usually have a table, crown, girdle, pavilion and culet just as diamonds do.

Unlike diamonds, gemstones do not have a geometrically ideal cut to maximize brilliance. For gemstones, a high-quality cut exposes the fewest inclusions, displays the majority of the gemstone weight when set in jewelry and presents the most even color.

When the cut is ''shallow'' we can see what we call a window in a color gemstone. The body color appears to be watery. It causes light to leaks out from the main body. Extension is the name used when the color gemstones are cut with extremely deep pavillon. It will make the body color look darker.

A well-cut gemstone is symmetrical in all dimensions. It appears balanced and its facets reflect light evenly across the surface, providing good brilliance. It is eveluated by looking at the stone face up and determinating the percentage of light returned. The polish is smooth, without any nicks or scratches.

Its cut affects the depth of a gemstone’s color. The deeper the cut, the deeper the color. In a gemstone with more saturated color, a shallow cut will permit more light to penetrate, while in a less saturated gem, a deeper cut may increase its vividness.

A sapphire or ruby should not display the bands of color common to corundum crystals. If it does show these streaks, the gem was cut for maximum weight rather than beauty.

Cut

Diamonds mined from the earth look like tumbled gems or beach glass. To turn the diamond into a beautiful gem, the diamond is cut with precise facets, or tiny polished faces. There are 58 total facets on the round brilliant diamond: 33 facets are in the crown and table (largest facet) located above the girdle (the diamond’s widest point), 24 facets in the pavilion and 1 facet at the bottom, or culet.

A well cut diamond will have an amazing brilliance and fire. This is caused by white light reflecting off the diamond’s surfaces and the mirrored depths of the pavilion. The key to desirable fire and brilliance is proportion. Light striking a shallow cut diamond will fall out the other side and not reflect back to the top. Light striking a deep cut diamond will get lost in the pavilion and also be unable to reflect back to the top.

 

Quality in Colored Gemstones The appearance of a colored gem is a combination of many separate factors, each of which is related to, and affected by, the others. It is precisely the complexity of these intertwined relationships that has bedeviled all attempts to quantify quality. And yet, every time a dealer buys a gem, a quick mental analysis is made, usually within seconds. In grading any gem, one must be cognizant of, but not become lost in, the details. When all the minutiae has been pored over ad infinitum, take a step back and simply look at the gem. In the age of high-powered microscopes this may constitute a radical concept, but one which is necessary.

In the following essay, we will examine in detail the features that make up a fine colored gemstone.

The Four C’s Determining the quality of a gemstone involves what jewelers refer to as the “four C’s”. They are as follows:

1. Color 2. Clarity 3. Cut 4. Carat Weight

To these, we can also add a fifth C, Color Coverage. While these factors are well defined for diamond, no universally-accepted system exists for

colored gems.

Color: The First C For a colored stone (any gem other than diamond), color is the most important factor in determining quality.

To the color scientist, given an opaque, matt-finished object, there are three dimensions to color:

Hue position Saturation (intensity) Tone (lightness or darkness)

For colored gemstones, there is also a fourth factor:

Color coverage

Left: Three-dimension view of a color solid. Illustration courtesy of Minolta USA. Right: Hue position describes the position of a color on a color wheel. Illustration © R.W. Hughes

The relationship between tone (lightness) and saturation. Illustration © R.W. Hughes

Hue position. The position of a color on a color wheel, i.e., red, orange, yellow, green, blue and violet. Purple is intermediate between red and violet. White and black are totally lacking in hue, and thus achromatic (‘without color’). Brown is not a hue in itself, but covers a range of hues of low saturation (and often high darkness). Classic browns fall in the yellow to orange hues.

Generally speaking, gems with hues that most closely resemble the red, green and blue (RGB) sensors in our eyes are most popular. Thus the colored gem trinity, ruby, emerald and sapphire. But there is much about hue that is a personal preference and will depend upon an individual’s personal taste.

Three green gems, showing a variation in hue position. The round center stone is a straight green, while the trillion-cut stone at left is a more yellowish green and the oval stone at right a slightly bluish green. Generally speaking, hue position is of less importance than saturation. Photo: Wimon Manorotkul

Saturation (intensity). The richness of a color, or the degree to which a color varies from achromaticity (white and black are the two achromatic colors, each totally lacking in hue). When dealing with gems of the same basic hue position (i.e., rubies, which are all

basically red in hue), differences in color quality are mainly related to differences in saturation, because humans tend to be more attracted to highly saturate colors. The strong red fluorescence of most rubies (the exception being those from the Thai/Cambodian border region) is an added boost to saturation, supercharging it past other gems that lack the effect.

Four blue sapphires showing a variation in saturation and tone. Stone 1 possesses a light tone and low saturation. Stone 2 is close to ideal in both tone and saturation. Stone 3 has greater saturation than Stone 2 in some areas, but its overall tone is too dark and it shows too much extinction. Stone 4 is so dark in tone that its saturation is reduced. Note that inclusions are far more visible in stones of light tone than those of dark tones. Photo: Wimon Manorotkul

Tone. The degree of lightness or darkness of a color, as a function of the amount of light absorbed. White would have 0% darkness and black 100%. At their maximum saturation, some colors are naturally darker than others. For example, a rich violet is darker than even the most highly saturated yellow, while the highest saturations of red and green tend to be of similar darkness. Note that as saturation increases, so too does tone (since more light is being absorbed. However, there reaches a point where increases in tone may result in a decrease in saturation, as a color “blackens.”

When judging the quality of a colored gem, tone is an important consideration. Before buying, it’s always a good idea to consider the lighting conditions under which it will be worn. Look for stones that look good even under the low lighting conditions you find in the evening or in a restaurant, for these are typically the conditions under which fine gems are worn and viewed. Also view gems at arm’s length and look for those that are attractive even at a distance. Exceptional gems will look great under all lighting conditions and viewing distances. (back to top)

Clarity: The Second C Clarity is judged by reference to inclusions. Magnification can be used to locate inclusions, but with the exception of inclusions which might impact durability, only those visible to the naked eye should influence the final grade. In this way, colored gems are very different from diamond. Indeed, in certain cases (Kashmir sapphires being a classic example), the inclusions can actually enhance beauty and value.

Different levels of clarity are visible here in these spessartine garnets from Nigeria. The oval stone at left is eye clean, i.e., with no clarity defects visible to the unaided eye. In the pear-shaped middle stone, obvious clarity defects are visible, while in the trillion-shaped stone at right, they are even more obvious. Photos: Wimon Manorotkul

There are two key factors in judging clarity. These are:

Visibility of inclusions

Size: Smaller inclusions are less distracting, and thus, better. Number: Generally, the fewer the inclusions, the better. Contrast: Inclusions of low contrast (compared with the gem’s RI and color) are less

visible, and thus, better. Location: Inclusions in inconspicuous locations (i.e., near the girdle rather than

directly under the table facet) affect value less. Similarly, a feather perpendicular to the table is less likely to be seen than one lying parallel to the table.

Impact on durability

Type: Unhealed cracks may not only be unsightly, but also lower a gem’s resistance to damage. They are thus less desirable than a well-healed fracture. As already mentioned, tiny quantities of exsolved silk may actually improve a gem’s appearance, and thus, value.

Location: A crack near the culet or corner would obviously increase the chances of breakage more than one well into the gem. Similarly, an open fracture on the crown is more likely to chip than one on the pavilion. Inclusions in certain positions may also reflect, making a single inclusion visible throughout a gem.

Note that cabochon-cut gems generally have poorer clarity than faceted gems. This is because inclusions are more visible in faceted stones than in cabs. (back to top)

Cut (‘Make’): The Third C The function of the cut is to display the gem’s inherent beauty to the greatest extent possible. Since this involves aesthetic preferences upon which there is little agreement, such as shape and faceting styles, this is the most subjective of all aspects of quality analysis.

The parts of a faceted gem. Photo: Wimon Manorotkul

Evaluation of cut involves five major factors (in no particular order):

1. Shape 2. Cutting style 3. Proportions 4. Symmetry 5. Finish

Shape. This describes the girdle outline of the gem, i.e. round, oval, cushion, emerald, etc. While preferences in this area are largely a personal choice, due to market demand and cutting yields, certain shapes fetch a premium. For most colored stones, ovals and cushions are the norm. Rounds and emerald shapes are more rare, and so receive a premium from about 10–20% above the oval price. Pears and marquises are less desirable, and so trade about 10–20% less than ovals of the same quality. The shape of a cut gem almost always relates to the original shape of the rough. Thus the prevalence of certain shapes, such as ovals, which allow greatest weight retention.

Shapes (girdle outlines). Illustration © R.W. Hughes

Cutting style. The cutting style (facet pattern) is also a rather subjective choice. Again, because of market demand, manufacturing speed and cutting yields, certain styles of cut may fetch premiums. The mixed cut (brilliant crown/step pavilion) is the market standard for ruby and sapphire, while the step (emerald) cut is the standard for emerald.

Proportions. The faceted cut is designed to create maximum brilliance and scintillation in the most symmetrically pleasing manner. Faceted gems feature two parts, crown and pavilion. The crown’s job is to catch light and create scintillation (and dispersion, in the case of diamond), while the pavilion is responsible for both brilliance and scintillation. Generally, when the crown height is too low, the gem lacks sparkle. Shallow pavilions create windows, while overly deep pavilions create extinction. Again, proportions often are dictated by the shape of the rough material. Thus to conserve weight, Sri Lankan material (which typically occurs in spindle-shaped hexagonal bipyramids) is generally cut with overly deep pavilions, while Thai/Cambodian rubies (which occur as thin, tabular crystals) are often far too shallow.

Depth percentage: In attempting to quantify a gem’s proportions, reference is often made to depth percentage. This is calculated by taking the depth and dividing it by the girdle diameter (or average diameter, in the case of non-round stones). The acceptable range is generally 60–80%.

Length-to-width ratio: Another measurement that is used for non-round stones is the length-to-width ratio. Overly narrow or wide gems of certain shapes are generally not desirable.

If a gem is cut too shallow, light will pass straight through, rather than returning to the eye as brilliance. This is termed a “window” (right). In well-cut gems, most light returns as brilliance (left). Brilliant areas are those showing bright reflections. Extinction is used to describe dark areas where little or no light returns to the eye. Photo: Wimon Manorotkul

Symmetry. Like any finely-crafted product, well-cut gems display an obvious attention to detail. A failure to take proper care evidences itself in a number of ways, including the following:

Asymmetrical girdle outline Off-center culet or keel line Off-center table facet Overly narrow/wide shoulders

(pears and heart shapes)

Overly narrow/deep cleft (heart shapes)

Overly thick/thin girdle Poor crown/pavilion alignment Table not parallel to girdle plane Wavy girdle

Finish. Lack of care in the finish department is less of a problem than the major symmetry defects above, because it can usually be corrected by simple repolishing. Finish defects include:

Facets do not meet at a point Misshapen facets Rounded facet junctions Poor polish (obvious polishing marks or scratches)

Scintillation (‘sparkle’). This is an important factor in faceted stones. A gem cut with a smooth, cone-shaped pavilion could display full brilliance, but would lack scintillation. Thus the use of small facets to create sparkle as the gem, light or eye is moved. In general, large gems require more facets; small gems should have less, for tiny reflections cannot be individually distinguished by the eye (resulting in a blurred appearance).

Dispersion (‘fire’). This involves splitting of white light into its spectral colors as it passes through non-parallel surfaces (such as a prism). While diamonds show this property to great effect, with most colored stones, their dispersion is too low and the masking effect of the rich body color so high, that it is not generally a factor. Exceptions are gems such as demantoid garnet, grandite garnet from Mali and sphene. In gems such as these, a weaker body color can actually be desirable, making the fire more visible.

Summing up cut. While these guidelines may be useful, one must not become a slave to them. In essence, the cut should display the gem’s beauty to best advantage, while not presenting setting or durability problems. If the gem is beautifully cut, things such as depth percentage or length-to-width ratio matter not one bit. What works, works. The eye, the mind and the heart are the final arbitrators, not numbers.

One final note about cut. The most expensive colored gems (particularly colored diamonds and rubies) often feature misshapen proportions and symmetry. This is because the value of the material is so high that the cutter strives to save every point in weight. (back to top)

Carat psychology

In the case of many gems, including ruby and sapphire, psychological (but all too real) price jumps occur at certain weights. For example, a 0.99-ct ruby might be worth significantly less than one which weighs 1.05 ct. The 1.05 ruby would be worth more than one which weighed exactly 1.00 ct, as repolishing a 1.00-ct stone (or weighing it on someone else’s scale) might send it below the important 1-ct barrier. Similar psychological weight hurdles are found at the 2, 5, 10, 20, 50 and 100-ct levels.

Above. Graph representing the

Carat Weight: The Fourth C Weight in gems is calculated in metric carats, where five carats equal one gram. Generally, as a gem’s weight increases, so does the per-carat price. Such a relationship has long been known, and was first quantified by Villafane in 1572, for diamonds. Today it is most commonly referred to as the ‘Indian Law’ or ‘Tavernier’s Law’, and works as follows:

Wt2 x C = price per stone Weight of gem = 5 ct (Wt) Cost of a 1-ct gem of equal quality = $1000 (C) 5 x 5 x 1000 = $25,000 total stone price

The following shows how the price of a gem might increase with this formula applied using a $1000/ct base price.

Weight Total stone

price

1 ct $1000

2 ct $4000

3 ct $9000

4 ct $16,000

5 ct. $25,000

10 ct. $100,000

Unfortunately, things were not so simple, even for diamonds in the time of Tavernier. The law could not accurately predict the price of diamond below 1 ct, and there were also problems with exceptionally large stones. But it does give a general idea of how prices increase with size. (back to top)

Color Coverage: The Fifth C With gems, we are not dealing with opaque, matt-finish objects of uniform color. Thus it is not enough to simply describe hue position, saturation and darkness. We must also describe the color coverage, scintillation and dispersion.

Differences in proportions, inclusions, transparency, fluorescence, cutting, zoning and pleochroism can produce vast differences in the color coverage of a gem, particularly faceted stones. A gem with a high degree of color coverage is one in which color of high saturation is seen across a large portion of its face in normal viewing positions. Tiny light-scattering inclusions, such as rutile silk, can actually improve coverage, and thus appearance, by scattering light into areas it would not otherwise strike. The end effect is to give the gem a warm, velvety appearance (Kashmir sapphires are famous for this). Red fluorescence in ruby boosts this still further.

relationship between price and quality/weight/rarity. Note that this is not a linear relationship. Price increases more quickly as quality/weight/ rarity increases. Illustration © R.W. Hughes

Color coverage can be influenced by a variety of factors, including proportions, fluorescence and inclusions. The round Burmese red spinel at left is strongly fluorescent and the red emission adds extra power to the red body color, covering up extinction. With the fine emerald-cut Kashmir sapphire pictured at right, color coverage is improved by the presence of tiny needlelike inclusions, which scatter light across the stone, thus reducing extinction. This is what gives Kashmir sapphires their incomparable velvety color. Note that both of these gems have colors which are highly saturate, making them highly desirable. Photos: Wimon Manorotkul, John McLean

Proper cutting is vital to maximize color coverage. Gems cut too shallow permit only short light paths, thus reducing saturation in many areas. Such areas are termed windows. Those cut too deep allow light to exit the sides, creating dark or black areas termed extinction. Areas which allow total internal reflection will display the most highly saturated colors. These areas are termed brilliance.

Color zoning can also reduce color coverage. Ideally, no zoning or unevenness should be present.

Color zoning can also be influenced by color zoning, an unevenness of color. The oval sapphire above shows moderate color zoning. Moderate to severe color zoning does impact quality, and thus price. Color zoning is always judged in the face-up position, in an 180° arc from girdle to girdle, with the gem rotated through 360°. Color irregularities visible only through the pavilion generally do not impact value. Photo: Wimon Manorotkul

Pleochroism is noticeable face-up in some gems, such as some tourmalines and iolite. It typically appears as two areas of lower intensity and/or slightly different hue on opposite sides of the stone.

The effects of pleochroism can clearly be seen in this oval green tourmaline. Along the vertical axis, a bluish green color is seen, while along the horizontal axis, the color is yellowish green. This is a product of the doubly refractive nature of tourmaline. Photo: Wimon Manorotkul

In summary, a top-quality gem would display the hue of maximum saturation across a large

percentage of its surface in all viewing positions. The closer a gem approaches this ideal, the better its color coverage. (back to top)

Enhancements The term “enhancement” is a treatment or process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, value or availability of a gemstone. In today’s gem marketplace, many gemstones have been enhanced by a variety of methods. Such processes may range from simple heating (such as with tanzanite) to high-tech irradiation (such as blue topaz).

Gems which have not been subject to enhancement are generally worth more than those of the same quality which have been enhanced. See this list for more on enhancements. Because enhancements affect value, it is vital that buyers be provided with full enhancement information when considering the purchase of any gem. (back to top)

Colored Stone Grading: Art or Science? Among the problems of existing colored stone grading systems is that the model chosen is based on diamond. While diamond does share a number of quality factors with colored stones, others are partly or wholly inappropriate. For example, beauty in diamond is largely a function of the material’s brilliance and dispersion (‘fire’). Any inclusions which alter the path of light could be detrimental to a diamond’s appearance. Perfect clarity is thus the ideal. As described above, perfect clarity is not necessarily the ideal for ruby and sapphire. While fractures and most other inclusions do have a detrimental effect on appearance and durability, small quantities of finely dispersed inclusions (such as exsolved rutile silk) can actually improve a richly colored gem’s appearance. The watchword here is small; too much silk decreases transparency by scattering, reducing color saturation, and thus producing a more grayish color.

Fine precious stones are comparable to great works of art. Like a painting, to appreciate it, one must view the whole, not just the parts. (back to top)

Precious vs. Semi-Precious In former times, gems were often divided into “precious” and “semi-precious” categories. The precious stones were:

1. Diamond 2. Ruby 3. Sapphire

4. Emerald

Semi-precious stones included everything else. While such categories were convenient, they ignored the reality that any precious stone can be cheap if the quality is low. In addition, some of the so-called “semi-precious” stones can cost tens of thousands of dollars per carat (Paraíba tourmaline, for example). Thus the terms “precious” and “semi-precious” have little meaning today with regard to value. Today, it is more common to separate gems into either diamonds or colored stones, rather than precious or semi-precious. (back to top)

Pricing Factors: Why They Don’t Always Make Sense

Prices of Genuine Jewels The prices of jewels are not stable. There is no law governing their prices, and there is no reason why these prices should not fluctuate with time and place. Each country, each nation carries its own temper. Furthermore, at one time nobles begin to sell them off and at others, to stock them. Stones are plentiful at one time and scarce at another. God grants honour to some and disgrace to others.

al-Biruni, 11th century AD Kitab al-Jamahir fi Ma‘rifat al-Jawahir

One of the great mysteries for the gem novice is the relationship between price and quality. In a perfect world, price would directly relate to quality/weight/rarity. Unfortunately, Planet Gem is far from symmetrical. Market factors can have as much, or even greater, impact on prices as does quality. Prices are influenced by the following factors:

Quality: Better qualities are more rare than lower qualities of the same size (see previous section).

Weight: Bigger stones are more rare, and so more expensive per carat than the same quality of a smaller size.

Market factors: This is the great intangible. Market factors can dramatically affect price.

Market factors Just a few of the market factors that influence price include:

Market supply vs. demand: Items which are plentiful and/or in low demand will be cheaper than those which are rare and/or in high demand.

Financial situation of the seller: Sellers who need money will obviously be more flexible on price. Similarly, those who are not in need are less willing to reduce their price.

Seller’s business overhead: Prices can vary dramatically depending on the seller’s overhead. A cup of coffee purchased by a street vendor may cost only a few cents; the same cup of coffee at a 5-star hotel in the same city may cost 10–20 times more, due to the hotel’s higher overhead.

Buyer’s financial situation: Buyers whose businesses are prospering are often willing to pay higher prices.

Buyer’s sales prospect: Buyers who have a customer waiting for an item are often willing to pay higher prices.

Buyer/seller personal relationship: No one likes to do business with unhappy or abusive people. When the buyer and seller enjoy each other’s company, they often make special provisions for one another.

Personal situation surrounding the sale: The author has seen buyers pay above-average prices for goods for a variety of reasons. These have ranged from trying to impress one’s girlfriend, to buying something simply to prevent a competitor from purchasing the same goods. (back to top)

Influence of Lighting on Color With any colored gemstone, the color seen depends on the light source used to illuminate it. Over time, gem dealers have come to rely on skylight for their gem buying. Its major advantage is its strength, which ruthlessly reveals flaws. The quantity of light coming through even a modest-sized window is far greater than even the strongest, color-balanced fluorescent tube (or tubes). Another factor appears to be the large radiating area, when compared with the most artificial lights.

Latitude may also affect a stone’s color, simply because skylight is stronger in the tropics. As a result, gems bought in the tropics will appear slightly darker when taken to more temperate climes. It is a slight, but nevertheless, noticeable difference. Surprisingly, north skylight (or south skylight in the southern hemisphere) is actually stronger on cloudy days.

Another factor is the Purkinje shift. In bright light, the eye is more sensitive to red; conversely, in dim light the eye is more sensitive to blue-violet light. Thus the color of blue sapphires would be slightly enhanced in dim lighting.

The question of north skylight. North daylight (skylight, as opposed to direct sunlight) has become the standard, because it produces the least glare, but blind adherence to such gemological dogma is just as bad as blind adherence to religious dogma. If you live north of the Tropic of Cancer (Europe, North America, Japan, China, etc.), north skylight will provide the least glare year round, because the sun always passes through the southern portion of the sky. This is especially true the farther north one goes. The opposite holds true for those who reside south of the Tropic of Capricorn (in the southern hemisphere), where the least glare is found using south skylight. Natural light is not constant in spectral composition, but varies according to latitude, time of day, cloud and pollution conditions and whether or not one is using direct sunlight or skylight.

Lighting can have a dramatic effect on the appearance of any colored gem. Incandescent lighting (left) is rich in red, orange and yellow wavelengths and thus pushes an object’s color in that direction. In contrast, skylight (right) is more balanced, pushing the color in the opposite direction. (Illustration: Minolta)

Above Left. The Buddhist temple at Swayambunath, Nepal, silhouetted against a deep blue sky. It is obvious that such skylight would enhance the appearance of blue stones.

Above Right. Fog in Sri Lanka’s central highlands. The high moisture content gives the light a grayish cast.

Right. Sunset on Sri Lanka’s western coast. While such sunlight could easily enhance the color of red and yellow stones, it should be noted that direct sunlight is rarely used for examining gems. (Photos © R.W. Hughes)

Typically we use skylight, instead. Such skylight is actually more blue early and late in the day. Thus blue sapphires will look better at those times. Conversely, when viewed with skylight, rubies will look best around midday, because the skylight is less blue.

What about those who live in the tropics? If they are north of the equator, north skylight is best, except May–July, when south skylight is preferred. For the tropics south of the equator, south skylight is best, except from Nov.–Jan., when north skylight is preferred. And if you live right on the equator, use north skylight from Oct.–Feb., and south skylight from April–August. During March and Sept., either north or south skylight can be used.

Time of day. Even skylight changes throughout the day. Generally speaking, rubies (and other red stones) look best during the midday hours. Sapphires, in contrast, look best in the early morning or late afternoon. If you are buying, this means that rubies should be purchased early or late in the day, while sapphires are best bought near midday, thereby preventing a

surprise when the stone is examined under another lighting condition. The above is in contrast to what is often reported. While direct sunlight is far more red at

sunrise and sunset, the skylight is actually more blue. Since we use skylight, not direct sunlight, to illuminate gems, blue color will be enhanced early and late in the day. Similarly, the skylight at noon is less blue, thus enhancing the color of rubies in the middle of the day.

Weather and pollution. How might clouds or pollution affect color? Heavily-polluted or cloudy skies will result in more grayish (less blue) skylight, thus improving the appearance of rubies (as opposed to sapphires).

Artificial lighting. Some type of artificial light is obviously the answer to neutralize the above factors. Many dealers today do their buying under special daylight lamps designed to simulate true north daylight, with a color temperature of approximately 5000–6100° Kelvin. Generally speaking, while their color balance is similar to north daylight, the fluorescent tubes used suffer from low light output. A 20-watt fluorescent daylight tube at a distance of 30 cm produces about 1000 lux of illumination, while a north-facing window in Bangkok averages 6000 lux. (back to top)

Viewing Geometry & Background Gems are designed to be mounted in jewelry and viewed from predetermined angles. This is generally face-up, with the gem viewed in a 180° arc from girdle to girdle. Thus it is only logical that all quality determinations be made with the naked eye under the same viewing geometry. It is important that the gem be rotated through 360° in the girdle plane, so that its appearance is seen from all angles, just as it would be when mounted in jewelry. To ensure reproducibility and repeatability, a standardized light source against a standardized, neutral background (white is best) at a standardized distance should be used. The practice in diamond grading of judging body color through the pavilion facets is madness, and has no place in colored stone grading.

Background checks

When you are examining a colored gemstone, act like a cop – always do a background check.

The color of the background against which a gem is examined can have a major effect on color. Which is why wily Burmese and Thai miners traditionally offer up rubies to buyers on brass plates or yellow table tops. The yellow background color counters the bluish tint commonly present in ruby, making the gems appear more red. Yellow cellophane-lined stone papers or brass tweezers serve the same purpose. Don’t be a sucker. For judging color, a plain white background is best.

Rubies and red spinels are typically traded on brass plates in Mogok, Burma. Photo © R.W. Hughes

 

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