When you’re shopping for a diamond, its brightness and sparkle will draw you to the jewelry counter, and keep you captivated long after you’ve made your diamond purchase. Achieving maximum brightness and sparkle requires excellent cutting technique, which is reflected in the diamond’s cut grade. Of the 4Cs, no other ‘C’ has more impact on a diamond’s appearance.

When people think of “cut,” they often think of the shape of a diamond rather than its cut quality. Cut is all about a diamond’s fire, sparkle, and brightness, and as a value factor, it refers to a diamond’s proportions, symmetry and polish; those factors that determine the cut quality or the fourth ‘C.’

In January 2006, GIA began assigning cut grades for round brilliant cut diamonds. Based on a comprehensive study that included 70,000 observations on more than 2,300 diamonds, GIA’s cut grading system assigns a diamond a grade of Excellent, Very Good, Good, Fair, or Poor.

A number of complex factors are considered when evaluating a diamond’s cut grade: its proportions, the symmetry of its facet arrangements, and the quality of its polish or finish. The cut grade reflects the diamonds appearance

In this post, we’ll focus on proportions – represented by the diamond diagram that appears on all GIA Diamond Grading Reports and GIA Diamond Dossiers. By learning about proportions, you’ll also learn the basics of a diamond’s anatomy, and gain an understanding of one factor that goes into setting a cut grade, determined from a combination of measured parameters.

Before we begin the Diamond Anatomy lesson, let’s be clear that no single proportion measurement is an indicator of what that diamond’s cut grade will be. GIA researchers proved that while every individual facet matters, a diamond’s appearance arises from the combined contribution of all its proportions. Even though all of a diamond’s parameters might be within the limits for a particular grade, a diamond might actually receive a lower cut grade when the parameters interact in a negative way to lessen a diamond’s appearance.

Therefore, for round brilliant cut diamonds, GIA considers how a diamond’s proportions relate to each other, rather than considering individual proportions in isolation.

Table Size: The table is the top horizontal facet of the diamond. The average table size is expressed as a percentage of the diamond’s average girdle diameter. While an ‘Excellent’ grade diamond will have a table size between 52 and 62 percent, other proportions are important too. Remember that GIA doesn’t consider individual proportions in isolation.

Total Depth: The diamond’s overall depth from the surface of the table to the culet, expressed as a percentage of the average girdle diameter.

Pavilion Depth: The pavilion is the lower portion of a diamond from the bottom edge of the girdle to the culet. The pavilion depth is expressed as a percentage of the average girdle diameter. A pavilion depth that’s too shallow or too deep will allow light to escape from the side or bottom of the stone. A well-cut diamond will direct more light upward through the crown.

Pavilion Angle: Pavilion angle is another important dimension of the stone, especially as it relates to a diamond’s brightness. It is the average of the angles formed by the diamond’s pavilion main facets and its girdle plane. This should fall between 40.6 and 41.8 degrees to be considered “Excellent,” providing other parameters also fit their proper ranges.

Crown Height: The crown is the upper portion of the diamond, from the top edge of the girdle to the table. The average crown height is expressed as a percentage of the average girdle diameter. It can affect both the dispersion and brightness of a diamond.

Crown Angle: The crown angle is the angle that’s formed where the bezel facets meet the girdle plane. The crown angle in a well-cut diamond will be within 31.5 to 36.5 degrees. The crown angle has a large effect on the face-up appearance of a round brilliant cut diamond. The best range of crown angles provide a route for exiting light dispersion, as well as additional contrasting directions for entering light. Star Length: The horizontally projected distance from the point of the star facet to the edge of the table, relative to the distance between the table edge and the girdle edge. A well-cut diamond will range between 40 to 70 percent, when other parameters are within the correct ranges

Girdle Thickness: The girdle is the middle portion of a diamond, a narrow section separating the crown from the pavilion, and functions as the diamond’s setting edge. The girdle thickness is described as a range from its thinnest to thickest areas. A thick girdle is less desirable because it unnecessarily adds weight to the stone where it matters the least (making the diamond appear smaller). An extremely thin girdle is sometimes referred to as a knife-edge, and results in a diamond that is more fragile and susceptible to chipping. Therefore, a girdle that is “medium to slightly thick” is preferred.

Lower Girdle / Half Facet Length: This ratio is measured by calculating how long the lower girdle facets are relative to the length of the pavilion. This defines the contrast of a round brilliant cut diamond, which controls the brilliance of a diamond. The well-cut diamond will range between 65 to 90 percent. Diamonds with longer lower half facets will have a little more scintillation.

Culet: The culet is the small facet at the bottom of a diamond intended to prevent chipping and abrasion to the point. The culet size can affect face-up appearance and it’s described as the average width of the facet. Size is expressed as none, very small, small, medium, slightly large, large, very large, and extremely large. When there is no culet, it is sometimes referred to as a pointed culet. Preferably the culet will not be visible with the unaided eye, and when described as none (no culet), very small or small on a GIA report, it falls in the excellent range.

Now that you understand diamond proportions, you’re one third of the way to learning about the factors that influence a diamond’s cut grade. We’ll cover finish, polish, and symmetry in later posts.

An “Excellent” in GIA’s cut grading system will tell you what most people prefer. However, our best advice as you shop around is to do what GIA researchers did – look at a number of diamonds. After all, beauty is in the eye of the beholder and your own eyes will tell you whether or not a diamond’s cut is right for you.

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The unique beauty and appeal of fancy cut diamonds make them the perfect choice for gifts of the season. Shoppers now have a wide array of choices, so there is something for every taste. In this installment of our 2013 Holiday Buying Guide series, you will learn about some of the special characteristics of fancy cut diamonds before you ever step into a jewelry store.If you’re already familiar with the 4Cs of Diamond Quality, you know how GIA grades the color and clarity of colorless diamonds, and how GIA evaluates cut for round brilliant cut diamonds. But if you don’t know the difference between diamond shape and diamond cut, you might want to take a quick refresher before reading on.

In selecting your fancy cut diamond, it will be important for you to know if the diamond is well cut. If it is too shallow, there could be a greater risk of chipping the diamond. If it is too deep, it may appear to be less bright. While GIA does not grade the overall proportions of fancy cut diamonds, a GIA Diamond Grading Report does contain an assessment of the diamond’s Finish, which includes Polish and Symmetry. When the report denotes these as “Excellent” or “Very Good,” it’s an indication of the diamond’s cut quality.

You don’t have to be a diamond expert, but understanding the distinct features of each shape will help to ensure a smart purchase.

OVAL:

Oval is a shape that pairs well with other shapes of gems in multi-stone rings. Ovals have the added benefit of appearing larger because of their elongated shape. When selecting an oval diamond, look for even, well-rounded shoulders.

Your personal preference will likely decide which width of oval is more appealing, however the optimal length-to-width ratio is 1.33-1.66:1.

Ovals cut in the brilliant style display a brightness similar to round brilliant cut diamonds. Oval brilliant cut diamonds often display a “bow-tie.” Seen with the naked eye, this is a dark area which looks like two triangular pieces joined in the center of the stone. When the diamond is viewed face-up, you want the “bow-tie” to be minimized as much as possible.

Oval Diamond

MARQUISE:

Symmetry is an important factor for all fancy cut diamonds. Even the smallest difference can create an appearance that is not balanced. Check that each half is a mirror image of the other, and for marquises that the two points align. Like oval, this shape pairs well with other gem shapes in multi-stone rings, and if a prong mounting is chosen, V-shaped prongs will help protect the points.

If a marquise shape is too long, it could impact its durability. Look for a length-to-width ratio of 1.75-2.25:1.

Like the oval, the marquise diamond that is cut in the brilliant style should be examined for a “bow-tie” effect, and the points of the marquise should be examined for inclusions.

Marquise Shaped Diamond

PEAR:

Like all fancy cut diamonds, the pear diamond comes in a variety of proportions, however the preferred length-to-width ratio should range between 1.50-1.75:1.

Examine the point for inclusions and color concentration. The wings on each side of the point should be symmetrical. The rounded end should appear like a semi-circle. As with the oval and marquise, the pear brilliant may show a “bow tie.”

If a prong setting is chosen, it should include a V-shaped prong at the point because that will help protect it from damage.

Pear Shaped Diamond

HEART:

An obvious symbol of love and romance, the heart-shaped diamond should have two identical halves, and the cleft should be distinct. The wings and lobes need to be even with the lobes curving down the cleft.

The ideal length-to-width ratio is approximately 1.00:1. Check the point for any visible inclusions. As with the oval, marquise and pear, the heart shape may show a “bow tie.”

It may be difficult to perceive the heart in a diamond of less than .50 carats. For smaller size stones, a bezel or three-prong setting better preserves the shape.

Heart Shaped Diamond

TRIANGULAR:

You’ll often encounter triangular-shaped diamonds cut in the brilliant style, referred to by jewelers as trillion or trilliant. While this shape is sometimes set as a solitaire, it’s more commonly used as side stones in a multi-stone setting.

Attention should be paid to clarity, since even small inclusions may be more visible in this shallow shape. The preferred length-to-width ration is 1:00:1.

A protective prong setting is recommended to keep the sharp points from chipping.

Triangular Shaped Diamond

SQUARE:

Square diamonds are spotted almost daily on celebrity fingers this year. The halo setting used for brilliant cut square gems was one of the most popular engagement ring trends of 2013.

The list of cuts available for square shapes is a long one. Some of the trade names you may come across while shopping include Asscher, barion, cushion, princess, radiant and Quadrillion (as pictured below). All sides should be parallel.

Square Shaped Diamond

RECTANGULAR:

Similar to square shapes, there are numerous cuts for a rectangular look including baguette, barion, emerald cut, and radiant.

Avoid uneven, narrow or no corners and sides that are not parallel.

The emerald cut or a square step cut will require higher clarity since inclusions might be easier to see.

Rectangular Shaped Diamond

One general shopping tip for fancy cut diamonds is to view them in daylight. Pricing of the various shapes can be complicated, so it’s best to compare stones of the same shape, cutting style and similar carat weight. Ask to see the grading reports for the diamonds you are considering. They will help you compare each diamond’s quality factors.

For additional assistance on jewelry purchases this season, the 2013 Holiday Buying Guide series is a great resource to make you a more informed shopper.

Part 1: Diamond Jewelry Trends for the 2013 Holiday Season

Part 2: 4Cs Tips for Holiday Diamond Jewelry Shopping

Part 3: How to Read a GIA Grading Report Video

Part 4: Asking the Right Questions for a Diamond Purchase

The top image all weighing approximately one carat, represent a variety of shapes and cutting styles. From left: cushion, cut corner square step-cut, emerald, modified radiant, oval, marquise and pear. Photo by Robert Weldon/GIA.

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Diamond jewelry is often at the top of a woman’s holiday wish list but getting her a gift that she’ll love doesn’t have to be complicated. In the second installment of our 2013 Holiday Buying Guide series, you will learn the basics of what to look for when shopping for diamond jewelry.

The first thing to know is that not all diamonds are created equal. In fact, every diamond is unique, which makes buying a diamond seem all the more challenging. For starters, how do you compare them? To protect consumers and help everyone better understand diamond quality, GIA created the 4Cs, now globally accepted as the language used to describe diamond quality. The 4Cs are so universal that diamonds are valued by how they measure up to each of the Cs. Being familiar with the 4Cs not only helps you better appreciate each diamond’s unique beauty, but also understand its price.

Every woman knows ‘good things come in small packages’ and this short 4Cs primer will get you well on your way to making sure the gift you give her this holiday is one that will delight.

Color

GIA D-to-Z Color Grading Scale measures the degree of colorlessness of a diamond, as compared to a set of master stones of established color. D is the highest grade representing colorless. As you go down through the scale, the diamond is picking up more yellow or brown color. Colorless diamonds are the most rare, and their price will reflect their rarity. Even the slightest hint of color can make a dramatic difference in value. This interactive tool shows you the subtle differences in color.

Clarity

Few things in life are perfect, and diamonds are no exception. Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Clarity grades assess the number, size, relief, nature, and position of inclusions and blemishes. Flawless is the top grade in the GIA Clarity Grading Scale, and flawless diamonds are so rare that it’s possible to spend a lifetime in the jewelry industry without ever seeing one. There are 11 clarity grades assigned to a diamond, and the fewer inclusions and blemishes, the higher the value.

Cut

Cut is the finished shape of the gem and the number and angles of its facets. The GIA Diamond Cut Grading System for standard round brilliant diamonds (still the most popular diamond shape and cutting style) has five cut grades ranging from Excellent to Poor and takes into consideration not only the proportions, polish and symmetry, but also visual appearance. Many people mistakenly use the term “cut” to refer to the diamond’s shape. Diamond shapes other than round brilliant are called fancy shapes, and include marquises, pears, ovals, hearts, and triangles to name a few.

Carat Weight

As most people know, diamonds are priced by weight. Diamonds are weighed to a thousandth (0.001) of a carat, which is 0.200 grams, and then rounded to the nearest hundredth, or point. These exact calculations are important; fractions of a carat can mean price differences of hundreds—even thousands—of dollars. Only one in 1,000 diamonds is more than a carat, and this rarity means that larger diamonds of the same quality are worth more per carat. In other words, a two-carat diamond will often cost more than the total of two one-carat diamonds, because of a higher per carat cost.

Going to a jeweler with a basic understanding of the 4Cs will help tremendously in your ability to compare diamonds and talk knowledgably with the salesperson.

For even more information, GIA created the 4Cs app, available for iPhone, iPad and Android ®, which includes videos and interactive tools explaining each of the 4Cs in greater detail. It also has a useful tool called “My Diamond Wish List” where you can save and compare GIA-graded diamonds from different jewelers as you’re shopping this holiday season.

Now that you have a basic understanding of the 4Cs, you’ll want to know how to make sure the diamond you’re buying has the qualities you’re looking for. For more about GIA grading reports, stay tuned for the next installment in our 2013 Holiday Buyers Guide.

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Next up in GIA’s 4Cs Q&A series is diamond cut grading.

Q: How does pavilion depth affect a diamond’s cut?

A: The distance from the bottom edge of the girdle to the culet is the pavilion depth. A pavilion depth that’s too shallow or too deep will allow light to escape from the side of the stone and or leak out of the bottom. A well-cut diamond will direct more light through the crown.

Q: Why doesn’t GIA offer a cut grade for fancy-shape diamonds?

A: Establishing quality parameters for fancy-shape diamond cuts is extremely complex–much more so than for round diamonds because of the greater variations in shape–and measuring technology needs to progress far enough to capture the features considered important for fancy shapes. GIA is committed to developing a system that is accurate, comprehensive, and practical.

Q: How is diamond cut evaluated for standard round brilliant diamonds?

A: GIA uses sophisticated optical measuring devices to capture the measurements of those facets that influence the diamond’s face-up appearance. A diamond’s cut grade is established by comparing these measurements against a database of more than 38.5 million proportion sets of known grades and by the visual observations of polish and symmetry by GIA expert graders.

To read more about how a diamond’s cut is evaluated, please visit our 4Cs of Diamond Quality website or download the GIA 4Cs app, now available on iPhone, iPad, and Android!

Color Q&A | Clarity Q&A | Cut Q&A | Carat Weight Q&A

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As seen during the 2013 Oscars, vintage jewelry and diamonds continue to live in the spotlight, as evidenced by the Fred Leighton 19th Century oval and cushion cut diamond bracelet worn by Jennifer Aniston. But do you know the storied history behind your favorite vintage diamond cuts?

Centuries ago, diamond cutting was a slow process. The less material the cutter removed from the original rough diamond crystal, the more quickly he completed his work. Diamond cutters wages were penalized if they took too long or removed too much material. Therefore, the typical cut during this time was actually a squarish, sometimes slightly oval cushion-brilliant, or what most in the jewelry industry now refer to as an “old mine cut.” The defining characteristics are an often squarish shape and the diamond’s crown (top) and pavilion (bottom) are both much deeper than today’s standards.

Early mechanized, steam-driven factories in Amsterdam best illustrate how diamonds were cut in Europe and throughout the world at the time. Coster’s Amsterdam cutting house – in the mid-1800’s was the largest diamond cutting establishment in the world, still employed a labor-intensive process that included three phases of operation, each requiring workmen with specialized skills: 1) splitting or cleaving, 2) cutting, and 3) polishing.

Plot diagram.

Three events led to the more modern styles: in the 1870’s a “bruting” machine gave the diamond a round outline and the first angle gauges led cutters to use the angles associated with today’s modern cuts. In 1900 the circular saw came into use, making it far easier to split the typical octahedral-shaped diamond rough crystal into two pieces making it possible to cut the smaller top piece into a finished diamond, rather than just grinding it away. By 1902, many in the industry realized that using the saw saved weight from the common octahedral diamond crystals, which meant that the new proportions could be cut without expensive waste of diamond rough, shifting the emphasis from weight recovery to the beauty of the styles that we see today.

Natural yellow, old mine cut diamond.

These old-fashioned cutting techniques may have changed, but the gems from that era have a charm all their own, waiting for you to discover.

Discuss why you think vintage diamond cuts are a trend that is here to stay!

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Diamonds are renowned for their ability to transmit light and sparkle so intensely.

The quality of cut is crucial to the diamond’s final beauty and value. Of all the 4Cs, it is the most complex and technically difficult to assess.

The GIA Cut Grading System for the standard round brilliant diamond evaluates seven components. The first three, brightness, fire, and scintillation, consider the diamond’s overall face-up appearance. The remaining four, weight ratio, durability, polish, and symmetry, assess a diamond’s design and craftsmanship.

Brightness: Internal and external white light reflected from a diamond
Fire: The scattering of white light into all the colors of the rainbow
Scintillation: The sparkle a diamond produces, and the pattern of light and dark areas caused by reflections within the diamond

The design and craftsmanship of the diamond considers weight ratio (weight of the diamond relative to its diameter), the diamond’s girdle thickness (which affects its durability), the symmetry of its facet arrangement, and the quality of polish on those facets.Cut is oftentimes confused with the shape of the diamond. The most common diamond shape used in jewelry is the standard round brilliant. All other diamond shapes are known as fancy shapes. Traditional fancy shapes include marquise, pear, oval, and rectangular. Triangles and a variety of other shapes are also gaining popularity in diamond jewelry.

Has this post helped you better understand the difference between cut and shape? Coming soon, we wrap up our comprehensive guide to the 4Cs with must-have information about carat weight.

In the meantime, take a refresher course on diamond clarity, diamond color, and the Diamond Grading Scales.

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GIA created the 4Cs (Color, Clarity, Cut and Carat Weight) as a universal method for establishing the quality of any diamond, anywhere in the world. The 4Cs means two very important things: diamond quality can be communicated in a universal language, and diamond-buying consumers can know exactly what they are about to purchase.

All diamond images and diagrams are for reference only and may not reflect true diamond quality grade. Images are not for color or clarity diamond grading.

Interested in learning more about how to buy a diamond? Stay tuned for next week’s tutorial on diamond color or check out these great 1-minute videos on the 4Cs: Color, Clarity, Cut and Carat Weight.

The post GIA Diamond Grading Scales: The Universal Measure of Quality appeared first on GIA 4Cs Blog.

This guide will help you navigate and understand the relative quality differences that exist on the color, clarity and cut grading scales.

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One of the hardest of the 4Cs to understand may be a diamond’s cut. A well-cut diamond displays the unique sparkle we associate with diamond.

Many people often mistake a diamond’s shape (round, rectangular, oval) with its cut. But diamond cut is more than shape. A cut grade evaluates a diamond’s proportions, symmetry, and polish, which combine to deliver the magnificent return of light only possible in a diamond.

The diamond’s cut is crucial to a stone’s final beauty and value; however all of the 4Cs need to be taken into account when making a purchase decision. Learn about the next C, Diamond Carat Weight.

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Some diamond cut’s never go out of style, especially when they boast a royal heritage and have been redesigned and reinvented. Such is the case with the popular Asscher cut.

The Asscher cut was first developed in 1902 by Joseph Asscher, and became popular in the Art-Deco movement and following World War I. Although similar to an emerald cut, the Asscher cut’s 58 facets are larger and wide-set (three rows on the top, three rows on the bottom), and the stone is nearly octagonal in shape. Joseph Asscher saw an opportunity to better use rough diamond crystals to his advantage, therefore retaining more weight than the stone could with other styles of cutting.

Asscher Cut Earring

Because of the shape of the stone and the way the facets are cut, Asscher cut stones retain a classic appearance with a better balance of scintillation than a similar emerald cut, while still exhibiting a quieter aesthetic than a modern brilliant style cut.

Although the original Asscher cut is mostly seen in Art-Deco style jewelry from the early twentieth century, two very important (and world-renowned) gems carry the Asscher name. Originally cut from the same 3,105 ct. rough diamond by Joseph Asscher and Abraham Asscher, the Cullinan I diamond and the Cullinan II diamond are two of the most famous stones in the world. The pear-shaped Cullinan I, at 530.20 cts, sits atop the royal scepter in the British crown jewels, and the cushion-shaped Cullinan II (317.4 cts.) lies in the British imperial state crown.

Over the last ten years, it seems as though mentions of Asscher cut diamonds in popular bridal media has increased in the United States, which may be due to Edward Asscher’s redesign of the diamond. After visiting the GIA’s International Gemological Symposium in 1999 and realizing that the Asscher cut was still popular in the United State, Edward Asscher (grandson of Joseph Asscher, who created the original cut) returned to the Netherlands with an idea to craft a new, more dynamic species of Asscher cut diamonds, with even more brilliance and shine than before. The Royal Asscher cut diamond boasts 16 more facets than the original Asscher cut’s 58, allowing the diamond to catch light much better. Edward Asscher added two additional rows of eight facets each to the bottom of the stone, and subsequently making the rows narrower, he was able to keep the classic feel of his grandfather’s original cut while making the stone’s appearance more dynamic. With both the Asscher cut and the Royal Asccher cut, these angles and proportions used are critical to the beauty and brilliance of the diamond.

Nowadays, both the original Asscher cut and the Royal Asscher cut diamonds are popular, either in vintage jewelry stores or as new stones. Asscher cuts can often vary slightly in cut, proportions, and angles, as the cutter of the diamond decides the ultimate details of their rendition of the cut. However, the Royal Asscher cut boasts an international patent, meaning that the Royal Asscher Company limits the range of angles that can be used in cutting the diamond and is the only company allowed to cut a Royal Asscher stone.

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