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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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.

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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Angelina Jolie and Brad Pitt made headlines earlier this year when they finally announced their engagement. Soon thereafter, Jolie was spotted wearing an engagement ring that featured a large, Emerald cut diamond center stone. While an Emerald cut center stone is not the traditional look for an engagement ring, non-traditional engagement rings seem to be making news more frequently.

Many consumers admire the traditional outlines and understated elegance of an emerald cut diamond. The emerald cut is a type of step-cut diamond, and is the most popular in that category. The emerald cut’s four longer sides have beveled corners with two, three, or four concentric rows of facets, parallel to the girdle, on the crown and pavilion.

Emerald cuts do not hide imperfections well due to the long step cuts, so inclusions become more obvious in lower clarity diamonds. Emerald cuts can have 49 facets or more, yet are less scintillating due to the step cut style of faceting. Since lots of scintillation masks inferior color, this type of facet pattern with its lower scintillation seems to emphasize inferior color.

Remember, when shopping for an emerald cut diamond you need to choose the highest quality stone within your budget. Be sure to purchase from a jeweler that offers a GIA report with their diamond or request that a loose stone be submitted to GIA for grading.

Learn more about other diamond cuts and shapes with this great article, How Diamonds Shape Up.

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When it comes to diamonds, most consumers tend to use the words “cut” and “shape” interchangeably.  But for diamond professionals, there is a big difference.  Diamond Shape refers to the outline of the stone (pear, oval, round, etc.).  Diamond cut refers to a stone’s facet arrangement.  So a shape can be faceted in a variety of ways, or cutting styles. The most common facet arrangement, known as the brilliant cut, is applied to many shapes. It consists of 58 facets (if a culet facet is included) or 57 facets (if the culet is pointed). There will be one octagonal table, or top flat surface of the diamond and 16 kite-shaped facets and 40 triangular shaped facets and an optional small octagonal facet at the culet.

Round Shape

The round shape is the most popular, often used as a solitaire in engagement rings, earrings, or pendants. It’s estimated that 75% of all diamonds sold are round-shaped and according to research by The Knot, 53% of engagement ring center stones are round. The cutting style known as the round brilliant has been around since the 1700’s, but has been modified over the years.  The angles we see in today’s modern round brilliant – angles that help to enhance the diamond’s fire and brilliance – were first suggested by Henry Morse of Boston in the 1860’s and later slightly enhanced by Marcel Tolkowsky in 1919. In 2005,  a scientific way to assess — and help cutters plan and predict — the cut quality of round brilliant cut diamonds was introduced by GIA.

Oval Shape

The oval shape has probably the longest known history, with the first mention of an oval shaped diamond occurring in 1304:  the famous Koh-I-Noor, which now resides in the Tower of London. One of the most notable oval brilliant cut diamonds is the 184 carat Victoria, which was cut in 1887. The oval brilliant was popularized and modernized in the 1960′s. Containing fire and brilliance, the oval is suggestive of the round shape but is more unique. This shape also creates an illusion that the finger is longer and slimmer. The oval can be narrow or wide, depending on personal preference.

Marquise Shape

The marquise shape was named in 1745 for the Marquise de Pompadour, mistress of Louis XV of France.  The long and narrow shape, said to resemble the shape of the Marquise’s mouth,  creates an illusion that the diamond is of greater size. Symmetry is quite important with this shape, as even the slightest difference can create and uneven, imbalanced look.

Pear Shape

The pear shapes trace their history to the 1400’s, with the brilliant style being added in the 1700’s.  Pears have gently rounded shoulders and wings (the sides near the point) for an appealing outline. The point should always be directed out toward the fingers of the wearer, and the shape has a slimming effect on the hand. This shape is similar to the marquise shape, in that symmetry is extremely important.

Emerald Cut

An octagonal shaped diamond, the emerald cut was designed to highlight the qualities of emeralds. This cut is highly coveted due to its square or rectangle table-top cut and step-cut facets. The emerald cut’s smoothly beveled corners add visual appeal and provide a secure setting area for the prongs. This cut results in a more mirror-like look and requires a stone of very high quality.

Square shaped diamonds include the princess cut and quadrillion cut.  These cutting styles were created in the 1980′s and are also very popular cuts for engagement rings. The square shape creates the illusion of a larger diamond.  A princess or quadrillion cut diamond should always be set with prongs that protect the four corners–the areas most prone to chipping.

Among other square or rectangular shaped diamonds, some of the most notable cutting styles include:

The cushion cut. The brilliant style has been around since the mid-1700’s, it was the most common cut until the early 20^th century. Originally designed to retain as much weight from the original crystal as possible, this brilliant cut combines a square cut with rounded corners (much like a cushion). Antique dealers are often on the lookout for the older version of these diamonds, as their light patterns tend to be chunkier and more distinctive than modern-cut diamonds.

The radiant and barion cuts. Perfected around in the 1970’s, these create vibrant and fiery diamonds, ideal as a center-stone surrounded by smaller diamonds.

The baguette cut. Named for the French word baguette, which means “long rod,” this cut became popular during the 1920′s, an era when the Art Deco movement encouraged geometric shape and symmetrical flow. This cut is generally used for smaller side stones. They are often measured by dimensional size, rather than carat weight.

The Asscher cut.  Developed in 1902 and named after its creator, Joseph Asscher. It was also a popular cut for Art Deco jewelry. It is similar to the emerald cut, though it differs in that its facets are larger and it tends to be square rather than rectangular. Around 2002, this cut became popular again as modifications were made to the cut.

Heart Shape

The heart shape diamond can be a beautiful symbol of love and romance. A skilled cutter creates the heart shape, always keeping an eye on the heart’s balance and symmetry. This shape is ideal as a pendant and is very popular around Valentine’s Day.

Last, and by no means least, triangular shaped diamonds first made their appearance in the 1500’s. Brilliant cut versions of this shape gained popularity in the 1960’s with the appearance of a variation called Trillion. In 1978 an additional variation called the Trilliant came on the market. It was developed as a triangular version of the square-shaped radiant diamond and is sometimes considered an adventurous and provocative diamond choice.

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When a diamond interacts with light, every angle and every facet affects the amount of light returned to the eye. The sparkle of a diamond, then, has everything to do with how well the cut of the diamond was planned and executed. Although a diamond’s value is based on its unique combination of color, clarity, cut, and carat weight (the 4Cs), a diamond’s cut is the most complex to assess, and it’s the only component that can be directly affected by the diamond cutter.

Because there are so many variables and options to consider when cutting a diamond, the diamond cutter’s choices (whether man or machine) can produce two otherwise identical diamonds with vastly different levels of beauty, quality and value. This is particularly true of the standard round brilliant cut diamond.

After years of scientific research and real-life observation, GIA researchers proved that while every individual facet matters, a diamond’s appearance arises from the combined contribution of all its proportions. Therefore, for round brilliant diamonds, GIA considers how a diamond’s proportions relate to each other, rather than considering individual proportions in isolation.

GIA’s cut grade also considers the design and craftsmanship of the diamond, including its weight relative to its diameter, its girdle thickness (which affects its durability), the symmetry of its facet arrangement, and the quality of polish on those facets.

A magnificent diamond achieves its beauty through three optical effects:  Brightness (sometimes mistakenly called “Brilliance), Fire, and Scintillation.

• Brightness refers to all the diamond’s internal and external reflections of white light.
• Fire is the word used to describe the flashes of color you see in a polished diamond.
• Scintillation describes the flashes of light and the contrasting dark areas you see when the diamond, the light, or the observer moves—a combination of sparkle (spots of light) and pattern (arrangement of lights and darks).

The diamond cutter’s decisions determine these three optical effects, and when taken together with the color, clarity, and carat weight produce an individual grade of quality for a buyer’s consideration.

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