Diamond Carat Size

Diamonds are sold by the carat (shown as ct.), which is actually a unit of weight, though most think of a carat in terms of size. The word "carat" comes from the "carob" seed, the original unit of measure for diamond 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.

Two diamonds of equal carat weight can have very different costs based on other factors (such as cut, color, and clarity). In understanding the importance of carat weight, know thy partner. If the recipient's heart is set on a certain size diamond, then carat weight will probably be the most important factor in your search until the desired size is attained. At that point, other criteria will take on more importance. Most women can tell you the carat weight and shape of their ideal diamond, and most men can tell you the price.

As the carat size of a diamond increases, the diamond's price increases at an increasing rate. Why? Because the larger the diamond, the more increasingly rare it is. Fewer than one in one million mined rough stones are large enough to produce a finished 1 carat diamond. 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 diamonds of equal quality and increasing carat weights:

CaratWeight 1.00 2.00 3.00


$6,000 $12,000 $18,000


$6,000 $24,000 $54,000

Every Zodiacgems Diamond includes the price-per-carat so you can easily compare diamonds of various carat weights.

Looking For Earrings?

Choose from our assortment of hand matched Diamond Stud Earrings set in 14k gold.

Diamond Carat Size Chart

Even though the price of a diamond increases exponentially with the carat weight, the actual size does not. The table below illustrates the typical size relationship between diamonds of increasing carat weights. Note that when carat weight triples (from 1 to 3 carats), perceived size (represented in the images below) roughly triples as well, however the diameter increases only 45% (from 6.50 to 9.40), and crown area (the surface area visible when the diamond is set) slightly more than doubles.

CaratWeight 1.00 2.00 3.00



6.50 8.20 9.40

Crown (mm2)

33.2 52.8 69.4

Two 1 ct. diamonds: The diamond on the left has a deep cut and appears smaller from above

This is important to keep in mind when reviewing diamonds of any shape; a given increase in diameter will yield a larger increase in surface (crown) area and overall perceived size. While the third diamond above has a roughly 50% greater diameter than the first, it certainly appears more than 50% larger.

When viewing diamonds on Zodiacgems, check themeasurements listed for each diamond to understand its size. The length and width will tell you exactly how large the diamond will appear when viewed from above.

Two diamonds of the same shape and carat weight may still appear different in size based on the cut proportions. A deeply cut diamond has a greater proportion of its total weight "hidden" in the depth, resulting in a smaller diameter than a well cut diamond. These differences are usually small, but noticable. A well cut diamond may even have a slightly lower carat weight than a deeply cut diamond, yet still have a larger diameter, making it appear larger in size.

Diamond Carat Size Comparison

Two diamonds of equal carat weight may also appear very different in size based on the shape of the diamond. For instance, a 1 carat marquise tends to appear larger than a 1 carat round. The chart below illustrates why. For each diamond, the chart shows the following:

Approximate size

The diamond images shown are a very close approximation of the actual size of a 1 carat excellent cut for each shape. Visually, the longer shapes (oval, marquise, pear, emerald) tend to appear larger to the eye than the round and square shapes.

Measurements (Length x Width)

The measurements correspond to the shape shown above, and are typical for excellent cut diamonds of 1 carat weight.

Crown Area - The total surface area (mm2)

The area gives the true size of the diamond face up (as it would appear when set in a ring). For example, while the oval diamond image appears larger than the round image, the actual surface area is the same for the two shapes, meaning the difference in size is one of perception, not reality. In contrast, the oval not only appears larger than the princess cut, it actually has a larger surface area (approximately 10% larger in this example), meaning the difference is not simply an illusion created by the elongated shape.

Remember that while the measurements below are typical, every diamond is unique.














Crown (mm2)











To see the actual size of each diamond shape at various carat weights, print the diamond carat size chart below:

Printable Diamond Size Chart

Print a copy of our complimentary diamond size chart to see the actual sizes of diamonds of various shapes.

Diamond Certification and Grading

Before being purchased, many diamonds, and all Zodiacgems Diamonds (with the exception of our diamond stud earrings) are sent to a third party laboratory for a comprehensive evaluation; a process known as diamond certification. A reputable lab is one staffed by professional gemologists who specialize in diamond grading. Each diamond certificate issued is uniquely numbered, and corresponds to one individual diamond. From that point forward, the diamond and certificate (laminated to prevent tampering or damage) will travel together from seller to buyer.

Laboratory certification provides an impartial judgment of the characteristics and quality of each diamond. This certification (called a grading report, or dossier by GIA) gives the purchaser added confidence that the diamond received is as described by the seller. The diamond certificate is also valuable for insurance purposes, as it provides a professional, independent evaluation of the diamond.

A laboratory certification is not an appraisal. An appraisal seeks to establish the value of an item, mainly for insurance purposes. A diamond certificate does not evaluate a diamond's market value, only its characteristics and quality. That said, diamond certification from a reputable laboratory is invaluable in generating an accurate appraisal.

Gia Certification

Zodiacgems sells only loose diamonds which have been certified by the Gemological Institute of America (we do offer uncertified diamond studs). GIA is the world's oldest, largest, and one of the most respected independent laboratories. Unlike some other labs, GIA is not owned or partially owned by diamond wholesalers or retailers, and is a non-profit organization. GIA actually developed the "4 C's" diamond grading system (used almost universally today) to provide truly objective standards in the evaluation of a diamond.

Every certified Zodiacgems Diamond is accompanied by its GIA Grading Report or Dossier. These diamond grading certificates may be viewed prior to purchase by clicking the name "GIA" next to the diamond.

Following is an overview of what each document contains:

Gia Diamond Grading Report

  • Date: The date the diamond was examined by GIA
  • Report Number: The unique tracking number assigned to each diamond and report.
  • Shape (e.g. brilliant round, square modified brilliant)
  • Measurements: to the nearest one-hundredth of a millimeter
  • Carat Weight: to the nearest one-hundredth of a carat
  • Depth %
  • Table %
  • Girdle Thickness
  • Culet Size
  • Polish Grade
  • Symmetry Grade
  • Clarity Grade
  • Color Grade
  • Cut Grade: for round diamonds only
  • Fluorescence Grade
  • Laser Inscription: Notes the content of any inscription present on the girdle of the diamond.
  • General Comments: Additional identifying characteristics or features not otherwise represented in the report.
  • Diamond Plot: showing all inclusions and blemishes found.
  • Proportion Diagram: A graphic representation of the diamond's actual proportions.
  • Security Features: A variety of document security features (such as hologram, security screen, micro-print lines) which confirm the authenticity of the report.

GIA Diamond Dossier

For smaller diamonds, an abbreviated form of the GIA Grading Report is often used, called a GIA Dossier. This condensed report offers the same information as the GIA Grading Report listed above, with the exception of a diamond plot, since the individual flaws are less important in smaller stones (as is clarity in general). Every diamond that has been issued a GIA Diamond Dossier will have the report number laser inscribed on the diamond's girdle. This added security allows the purchaser to confirm the identity of the diamond at all times.

A note of caution:

All Labs are not created equal, and their judgments are not held to any objective standard. Unfortunately, some labs have succumbed to pressure from retailers to lower their standards, thereby allowing lower quality diamonds to be certified with higher ratings, increasing their value in the marketplace. Before relying on any diamond certificate, make sure you are comfortable with the reputation and expertise of its author.

While Zodiacgems chooses to offer GIA certified diamonds, other labs which have a strong reputation in the marketplace include AGS (American Gem Society) and HRD (more common in Europe than the U.S). Diamonds with certification from labs such as IGI and EGL tend to sell at a small discount, since these labs are known for relaxed diamond grading standards (for example, a diamond graded G in color by EGL may only be graded H by GIA).

Use caution when comparing the price of diamonds graded by two different labs; what at first seems like a bargain may only be the result of more relaxed diamond grading.

Buying Tip:

Only buy diamonds which have been certified by a reputable lab. Do not accept certifications created by retailers, even if they claim to be GIA trained.

Keep your diamond certificate in a safe place. It provides invaluable security in the case of loss (helping to establish the quality and size of diamond required for equitable replacement), trade, or resale. Whenever the diamond must leave your possession (for example, to be cleaned), always let the party taking possession know you have a certificate. Knowing you can positively identify your diamond removes any temptation on the part of the third party to commit fraud (such as switching the diamond for one of lower quality).

A copy of your uniquely numbered GIA certificate is kept permanently on file with the GIA, and can be replaced at anytime if lost or destroyed.

Diamond Clarity Chart

Because they are formed deep within the earth, under extreme heat and pressure; virtually all diamonds contain "birthmarks"; small imperfections inside the diamond (called inclusions), or on its surface (called blemishes). Clarity refers to the degree to which these imperfections are present. Diamonds which contain numerous or significant inclusions or blemishes have less brilliance because the flaws interfere with the path of light through the diamond.

The position of an inclusion affects how easily it can be seen. Diamond cutters make every effort to cut a stone so that inclusions are not visible through the table of the finished diamond. The preferred position for inclusions is under the bezel facets or near the girdle because they are harder to see there.

Almost all diamonds are graded for clarity using the 11 point diamond clarity scale created by the GIA, including diamonds which were not actually graded by GIA (every Zodiacgems Diamond is GIA certified). In grading diamond clarity, the GIA considers the number, size, color, reflectivity, and position of every flaw visible under 10x magnification.

Below is the GIA diamond clarity chart with definitions, accompanied by further explanatory comments from Zodiacgems:

GIA Diamond Clarity Scale


No inclusions or blemishes are visible to a skilled grader using 10x magnification.


Extremely rare, less than 1 in 5000 jewelry quality diamonds are rated FL.

Questions about clarity or other aspects of a diamond? Ask a diamond consultant for answers. A consultant will answer any questions you have, and if you like, search for diamonds on your behalf that match your criteria. A consultant can personally review a diamond, and give you a report on it's clarity or other details. chat online, or email

Looking For Earrings?

Choose from our assortment of hand matched Diamond Stud Earrings set in 14k gold.

Diamond Plot

Because a photograph cannot capture the subtleties of clarity, GIA uses a diamond plot to map a diamond's interior and exterior flaws. A diamond plot is a graphic representation of every flaw that affects the overall clarity grade. The flaws are found under 10x magnification by a skilled grader.

Example GIA Diamond Plot: The Key To Symbols section shows the flaws in order of severity

While the plot shows the type and position of each flaw, the actual visibility of the flaw is communicated in the diamond Clarity Grade itself (i.e. two diamonds may have very similar plots, but very different Clarity grades, reflecting the actual severity and visibility of the recorded flaws).

Besides the plot, there is also a comment section on the certificate where additional clarity characteristics are often noted. These are usually too minor to be reflected in the plot itself. Between the plot and the comment section, all inclusions visible under 10x magnification are accounted for.

A note of caution:

A diamond plot does not reproduce the actual appearance of a diamond. For SI1 or lower grades, do not assume that a relatively clean plot indicates that there are no flaws visible to the naked eye. Often, a plot may carry only one or two markings, but these are so severe that they warrant a lower overall clarity grade.

By the same token, a cluttered plot may not mean the diamond is visually flawed. The diamond may in fact be flawless to the naked eye, since no single inclusion is severe enough to be seen (even though the cumulative effect of the flaws might warrant a lower clarity grade). When in doubt, speak to a diamond consultant, who will gladly review a diamond on your behalf.

Common inclusions and blemishes, as they are represented on the GIA diamond plot, are illustrated below. GIA uses the color green for surface blemishes, and red for internal inclusions. Sometimes the nature of the inclusion (if it reaches the surface, for example) calls for the use of both green and red. The color black is used to convey extra facets.

The standard GIA Grading Report includes a diamond plot, the abbreviated GIA Dossier (often used for diamonds under 1 carat) does not.

A note of caution:

Before and After: Diamond Fracture Filling

Approximately 1 in 3 diamonds sold has been treated or "enhanced" in some way. A variety of techniques exist to artificially improve the natural clarity of a diamond. By drilling a pathway to an internal inclusion with a laser beam, acid can be poured into the tunnel to bleach the inclusion. The laser tunnel appears as a tiny white dot when viewed from the top of the diamond (where the drilling was performed), but as a long white line when viewed from the side. In addition, fractures in a diamond can be filled with a clear glass-like material, making them less visible. GIA will not certify diamonds which have been fracture filled.

While laser drilling and fracture filling are used to improve a diamond's clarity, high pressure / high temperature (HPHT) treatments are used to improve color by removing brown colorations from the diamond. HPHT involves placing the diamond in a pressure vessel and applying extremely high pressure and temperature. This environment mimics the conditions the diamond crystal was originally formed under. The effects of HPHT are permanent, and the presence of the treatment is very difficult to detect. GIA will certify a HPHT diamond, but will note the presence of the treatment on the diamond's certificate.

Any treatment or "enhancement" made to a diamond lowers its value.

Zodiacgems does not sell diamonds that have been treated in any way, including HPHT.

Buying Tip:

If you cannot tolerate imperfections, even those you cannot see, choose a VVS2 or better diamond. About 10% of all diamonds sold fall into this category.

The most popular range is the VS1-VS2 diamond. These diamonds appear flawless to the naked eye, and are a fraction of the price of a truly flawless diamond. Almost half of all diamonds purchased fall into this range.

The next most popular range is SI1, where the inclusions are usually not significant enough to impact the appearance of the diamond for the casual observer. Often, customers will opt for this clarity range in exchange for a higher cut or color grade. This combination often results in a beautiful, lively diamond with imperfections detectable only upon close inspection. In diamonds under 1 carat, the same can be said for an SI2 grade. In diamonds over 1 carat (where clarity is more important, and SI2 inclusions are often easier to detect), an SI2 is often half the price of a VS1 diamond. About one third of diamonds sold fall into the SI1-SI2 range.

If you are primarily concerned with size and price, I1 may be your best option. While the inclusions are visible to the unaided eye, many customers find it to be well worth the sacrifice for what it affords in size.

The larger the diamond, the easier imperfections are to detect; therefore Clarity becomes more important. For diamonds over 2 carats, a clarity grade of VS2 or higher is the safest bet for avoiding any signs of visible inclusions. In diamonds between 1 and 2 carats, clarity grades of SI1 or better will not have inclusions easily visible to the naked eye. In diamonds under 1 carat, clarity should be considered the least important of the traditional 4 Cs.

Brilliant-cut diamonds (such as round, princess, cushion, oval, pear, and marquise) hide inclusions better than step cuts (emerald, asscher). When purchasing a step-cut, move up one clarity grade (e.g. purchase a VS2 instead of an SI1 if you desire the lowest grade that has no visible inclusions).

If, while shopping for a diamond, you are ever given a clarity range (e.g. SI1-SI2) as opposed to a specific clarity grade, the diamond is not certified by GIA. The seller is only estimating the diamond's clarity using GIA terminology.

Diamond Color Chart

Diamonds come in a variety of colors, some of them highly prized (pinks, blues, even yellow). However in a white diamond, the presence of a yellow tint will lower the price of a diamond. The less body color in a white diamond, the more true color it will reflect, and thus the greater its value.

Every Zodiacgems Diamond has been assigned a color grade by the GIA in a viewing environment specially designed to eliminate color from surrounding surfaces as well as the light source itself. This allows the color of the diamond to be accurately measured. Minor differences in diamond color detected in this environment are very difficult if not impossible to detect in a normal environment. The diamond industry has adopted the GIA diamond color scale; almost every diamond sold today is rated using the GIA color scale, whether it was actually certified by the GIA or not.

Diamonds of D, K, and Z GIA Color Grade

The GIA grades diamonds on a scale of D (colorless) through Z (light color). All D-Z diamonds are considered white, even though they contain varying degrees of color. True fancy colored diamonds (such as yellows, pinks, and blues) are graded on a separate color scale.

Below is the GIA diamond color chart with definitions, accompanied by further explanatory comments from Zodiacgems:

GIA Grade Color Scale

While there are differences in color between D, E, and F diamonds, they can be detected only by a gemologist in side by side comparisons, and rarely by the untrained eye.

D-F diamonds should only be set in white gold / platinum. Yellow gold reflects color, negating the diamond's colorless effect.


The photo below shows a master set used by gemologists to grade color in diamonds. Each diamond to be graded is compared to the master set to determine where it should fall on the diamond color scale. The colors you see below are slightly exaggerated, since viewing diamonds face down makes their body color more pronounced. The face down orientation makes the detection of body color easier because brightness and fire are minimized when the diamond is face down.

This J color diamond appears whiter when set in yellow gold

Color becomes much harder to detect once a stone is set in a ring and placed in an environment that contains color (as opposed to the all white background used in diamond color grading). For instance, an H color diamond may look as colorless as a D when set in a ring under normal lighting conditions, especially if the two are not compared side by side.

Another factor that affects a diamonds's apparent color is the color of the mounting itself. Yellow gold makes slight amounts of yellow in a diamond less obvious, while white metal mountings make the color in yellow diamonds more apparent.

The vast majority of untrained observers (and many gemologists) cannot distinguish a color grade from the one just above or below unless the diamonds are compared side by side in a controlled environment.

Color becomes more important as carat weight increases, because color is easier to perceive in a larger diamond, just as a carafe of white wine shows more color than a single glass.

Questions about color or other aspects of a diamond? Ask a diamond consultant for answers. A consultant will answer any questions you have, and if you like, search for diamonds on your behalf that match your criteria. chat online, or send your request to

Looking For Earrings?

Choose from our assortment of hand matched Diamond Stud Earrings set in 14k gold.

Buying Tip:

For the best value in what would appear to the naked eye as a colorless diamond, look for G-J diamonds. Because color is easier to detect in larger diamonds, opt for G-H in diamonds over 1 carat, and I-J for those under 1 carat. Once set in a ring, these diamonds will look just like higher color grade diamonds. Instead of investing in higher color, invest in higher cut, the most important factor in a diamond's brilliance.

Because diamonds with more facets reflect more light, they tend to hide color better than other shapes. So, consider round, princess or other modified brilliant cuts over step cuts such as emerald or asscher if you are concerned about color.

If you are concerned primarily about carat weight, and are on a tight budget, consider a yellow gold setting and a round diamond in the K-L color range. A lower color diamond with a higher cut grade will have more sparkle and visual appeal than a higher color diamond with a lower cut grade.

If, while shopping for a diamond, you are ever given a color range (e.g. G-H) as opposed to a specific grade, the diamond is not certified by GIA. The seller is only estimating the diamond's color using GIA terminology.

Diamond Cut

Cut refers not to a diamond's shape (e.g. round, oval, pear, etc.) but to a diamond's proportions, symmetry and polish. The beauty of a diamond depends more on cut than any other factor. Though extremely difficult to analyze and quantify, diamond cut has three primary effects on appearance: brilliance (the brightness created by the combination of all the white light reflections from the surface and the inside of a polished diamond), fire (the dispersion of light into the colors of the visible spectrum, seen as flashes of color), and scintillation (the flashes of light and dark, or sparkle, when a diamond or light source is moved).

When a diamond is fashioned from a rough stone, the cutter must balance optimal cut (and therefore appearance) against maximum yield (cutting the diamond to maintain as much carat weight from the rough stone as possible). Because many customers are willing to pay more for a larger, fair-cut cut diamond than for a slightly smaller, well-cut diamond, there is pressure on the cutter to sacrifice appearance for weight. This is why the Cut grade is so important; it allows the purchaser to identify those stones that were cut Fair to Poor in an effort to gain carat weight.

At left, the same rough stone (shown in blue) can yield one of two potential diamonds:

A too-deep cut diamond (orange) would yield a significantly larger diamond, earning the diamond cutter a larger profit on his investment.

A smaller, well cut diamond (white) may sell for less in total than the larger diamond, but it will command a higher price-per-carat not only because of its superior appearance, but also due to decreased yield from the rough stone (which therefore makes the diamond more expensive to create).

Questions about cut or other aspects of a diamond? Ask a diamond consultant for answers. A consultant will answer any questions you have, and if you like, search for diamonds on your behalf that match your criteria. chat online, or send your request to

Looking For Earrings?

Choose from our assortment of hand matched Diamond Stud Earrings set in 14k gold.

Diamond Cut Proportions

Diamond proportion refers to the relationship between the size, shape, and angle of each facetof a diamond. A wide range of combinations are possible, ultimately determining the diamond's interaction with light.

When light strikes a diamond, approximately 20% immediately reflects off the surface (as glare). Of the 80% that enters, a portion will escape through the bottom of the diamond (where the observer cannot appreciate it). A well proportioned diamond will have each facet properly placed and angled so as to maximize the amount of light that reflects back out of the crown (top) of the diamond, to the eye of the observer. This reflected light is perceived as scintillation,fire and brilliance.

In the diagram below, three common light patterns are shown. When light meets any facet of a diamond, it will either reflect (bounce back) or refract (bend while passing through the facet). The angle that the light hits the facet determines whether the majority of light reflects or refracts, which is why cut is so important.

Shallow Cut

If the diamond cut is too shallow, entering light strikes thepavilion facet at a low angle and passes through the facet (refracts), escaping through the bottom of the diamond.

Deep Cut

If the diamond cut is too deep, entering light strikes the first pavilion facet at an angle sharp enough to reflect to the second pavilion. But the light strikes the second pavilion at too low an angle, causing the light to refract (pass through the facet), escaping through the bottom of the diamond.

Well Cut

In a well cut diamond, the light strikes each pavilion facet at an angle which allows most of the light to reflect back to the crown (top). As it passes through the crown facets at a low angle, the light refracts upon exit. In this case, refraction is a good thing, as the bent light travels to the observer's eye and is perceived as a lively fire.

Diamond Depth %

Depth refers to the distance between the culet and the table when the diamond is viewed from the side. Diamond depth is expressed in millimeters, and is given as the third number under "measurements" for every Zodiacgems Diamond (the first two numbers are length and width).

The depth % of a diamond is calculated by dividing the depth by the width of the diamond. So, if a diamond is 3 mm in depth, and 4.5 mm in width, its depth % is 66.7. The lower the depth %, the larger a diamond of a given carat weight will appear (since most of the diamond's size is in its width vs. in its depth).

Diamond Table %

The table % of a diamond is calculated by dividing the width of the table facet by the width of the diamond. So, if the table facet is 3 mm wide, and the diamond is 4.5 mm wide, its table % is 66.7.

A note of caution:

A diamond should not be chosen or rejected based solely on depth % or table %. Because the overall Cut grade already incorporates both factors, it should be used as the primary determinant when choosing a diamond. When comparing two diamonds of equal Cut grade, depth % and table % can then be used as further refinements, especially (in the case of depth %) if one is concerned about how large the diamond will appear.

Diamond Proportion Diagram

GIA Diamond Proportion Diagram

Every Zodiacgems Diamond comes with a GIA Grading Report or Dossier certificate, most of which include a proportion diagram. The proportion diagram is a graphic representation of the diamond's actual proportions.

The proportion diagram shows the diamond's girdle size, culet size, table and depth percentages, as well as other measurements, such as the crown and pavillion angles.

Each angle and dimension is measured electronically using a light scanner. The proportion diagram is a "fingerprint" of your diamond.

Excellent, Very Good, and Good GIA Cut Grades

Grading Diamond Cut

Evaluating the combined effects of facet shapes and angles, girdle width, culet size,polish and symmetry on the overall appearance of a diamond is a daunting task, even for professional gemologists. Fortunately, all of these factors have already been taken into consideration when calculating the diamond's Cut grade.

Because Cut grade provides a single rating which weighs the combined impact of all of the factors listed above on a diamond's visual performance, it is a simple yet vital tool in evaluating a diamond.

Cut grade should be a primary consideration when evaluating a diamond. Only when comparing two diamonds of identical Cut grade should the individual components of Cut (such as girdle width, symmetry, polish, depth%, table %, and culet size) be used as further refinements or tie breakers.

A note of caution:

Unlike the other "Cs" ( carat weight, color, and clarity), the various Cut grades in existence today were not originated by GIA, and are not uniformly applied. In fact, GIA has only been assigning cut grades since 2005, and only to round diamonds.

Even though retailers use common terms to describe Cut (such as Excellent, Very Good, Fair, Poor) the terms are not uniformly defined or applied. In fact, a diamond seller may assign any cut grade they choose, based on any set of factors they wish. One retailer will use terms such as "Signature Ideal", "Ideal", and "Excellent"; while another uses "Ideal" to describe all three, and another uses "Excellent" for all. Be cautious when comparing cut grades from different sources, as they are most likely inconsistent.

To avoid confusion or misrepresentation of any diamond, Zodiacgems uses the same cut grades as employed by GIA, and does not engage in "cut inflation" by creating other grades ("signature", "super ideal", etc.). Also, be aware of diamond sellers who assign their own cut grades in place of what GIA has already assigned to a particular diamond. Many popular websites and retail stores display their own, more generous Cut rating, in place of the GIA grade.

At Zodiacgems, the GIA cut grade is always shown. For diamonds without a GIA cut grade (because the diamond was certified before GIA began assigning cut grades in 2005, or is a shape that GIA does not currently assign cut grades to), Zodiacgems will apply its own cut grade according to a proprietary formula. Like GIA, the Zodiacgems cut grade is based on a variety of factors and is conservatively applied. In fact, when comparing our cut grade to that assigned by GIA, the Zodiacgems grade is equal to or lower than GIA 90% of the time.

Cut grade is assigned by the GIA (or Zodiacgems itself when there is no GIA grade), using the following scale:

Excellent Cut

Maximum fire and brilliance. Reflects nearly all of the light that enters the diamond, creating exceptional sparkle and life. of the diamond.

Very Good Cut

Properly reflects most of the light that enters the diamond, producing superior fire and brilliance. Under normal lighting conditions, appears very similar to Excellent Cut, but for a lower price.

Good Cut

Reflects a majority of the light that enters the diamond, for an above average appearance. An excellent value compared to higher cut grades.

Fair Cut

Allows much of the light entering the diamond to escape from the sides or bottom, reducing perceived fire and brilliance. More acceptable in diamonds of less than .75 carats, where differences in sparkle are more difficult to perceive.

Poor Cut

Allows most of the light entering the diamond to escape from the sides or bottom. The diamond may appear noticeably dull and lifeless, even to an untrained eye. Lumera does not offer Poor cut diamonds.

Excellent Cut

Questions about cut or other aspects of a diamond? Ask a diamond consultant for answers. A consultant will answer any questions you have, and if you like, search for diamonds on your behalf that match your criteria. chat online, or email

Buying Tip:

Cut grade is the most important factor in determining the overall appearance of a diamond, because a poorly cut diamond will seem dull even with excellent clarity andcolor. Conversely, a well cut diamond can have a slightly lower color (G-H) or clarity (SI1-SI2) and still look quite beautiful, due to its superior ability to create sparkle and brilliance.

For superior brilliance, choose a diamond with a Cut grade of Very Good or Excellent for round diamonds, and Good or better in fancy shape diamonds. When choosing a diamond in this range, make sure its Symmetry and Polish are Very Good or Excellent, so that the impact of the above average Cut is not obscured.

For those on a budget, primarily concerned with size, a diamond of Fair - Good cut may be an acceptable choice, especially in fancy shapes. While the diamond will lack the scintillation and brilliance of a well cut diamond, it will allow a significant increase in size for the same price.

Avoid Poor cut diamonds, even if size is the primary concern. Most find these diamonds to be an unacceptable trade off, despite the lower price. Zodiacgems does not offer Poor cut diamonds.

Diamond Shape

Virtually all diamond cuts sold for use in jewelry are one of ten round or fancy diamond shapes. The most popular diamond shapes are:

Following is an introduction to each shape, including information on how to determine the best combination of size, color, and clarity for your needs. View our side-by-side comparison of each diamond shape to see how shape affects apparent size as well.

Round Diamonds

The round cut diamond is the most popular diamond shape, representing approximately 75% of all diamonds sold. Due to the mechanics of its shape, the round diamond is generally superior to fancy shapes at the proper reflection of light, maximizing potential brightness.

Princess Cut Diamond

The princess cut diamond, first created in 1980, is the most popular fancy diamond shape, especially for engagement rings. Like round cut diamonds, princess cut diamonds are a good choice for their flexibility in working in almost any style of ring.

Oval Diamonds

Because the oval diamond is a modified brilliant-cut (like virtually all round cut diamonds), the two diamond shapes possess a similar fireand brilliance. However, oval cut diamonds have the added advantage of an elongated shape, which can create the illusion of greater size.

Marquise Diamond

The marquise cut diamond is a football-shaped, modified brilliant-cut. Because the marquise diamond is long and narrow, it can also create the illusion of greater size. Carat for carat, the marquise diamond has one of the largest surface areas of any diamond shape, making it a good choice when trying to maximize perceived size.

Pear Shaped Diamonds

The modified brilliant-cut pear shaped diamond is a combination of a round and a marquise shape, with a tapered point on one end. Ideally, a pear shaped diamond should possess excellent or very good symmetry. The point should line up with the apex of the rounded end. The shoulders and wings (the upper and lower curves on the right and left side of the diamond) should form uniform, symmetrical curves.

Cushion Cut Diamond

The cushion cut diamond combines a square cut with rounded corners, much like a pillow (hence the name). This classic cut has been around for almost 200 years, and for the first century of its existence was the most popular diamond shape (similar to round cut today). Refinements in cut have led to a recent resurgence in popularity.

Emerald Cut Diamonds

The unique look of the emerald cut diamond is due to the step cuts of its pavilion and its large, open table. Instead of the sparkle of abrilliant-cut, emerald cut diamonds produce a hall-of-mirrors effect, with the interplay of light and dark planes. Often, inclusions or bodycolor are easier to see in an emerald cut diamond.

Asscher Cut Diamonds

The asscher cut diamond was first produced in 1902 by the Asscher Brothers of Holland, an is a forerunner to the emerald cut. The asscher cut diamond is similar to the emerald cut, but in a square shape with larger step facets, a higher crown, and a smaller table. This combination often produces more brilliance than the emerald cut.

Radiant Cut Diamonds

The radiant cut diamond is the first rectangular cut to have a complete brilliant-cut facet pattern applied to both the crown and pavilion, creating a vibrant and lively diamond. The modified square shape is a nice bridge between a cushion and a princess cut, and for that reason looks beautiful set with both rounded or square cornered diamonds.

Heart Shaped Diamonds

The modified brilliant-cut heart shaped diamond is a unique and unmistakable symbol of love, popular in solitaire pendants as well as rings. Heart shaped diamonds less than .50 carats may not be a good choice, since the heart shape is more difficult to perceive in smaller diamonds, especially after they are set in prongs.

Buying Tip:

Most people who receive diamonds as a gift or for an engagement have a shape preference. While other factors (such as price and quality) should be determined by the purchaser, the choice of shape should include input from the recipient of the diamond, if at all possible. This is especially true for fancy shape engagement diamonds.