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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For many, jewelry shopping can be an intimidating experience. Add crowded malls, a long list of gifts to purchase, and the desire to get ‘just the right thing,’ and it can be downright stressful. But knowing what to ask a jeweler can help make this a great shopping experience

In part 4 of our 2013 Holiday Buying Guide, GIA put together the top five questions to ask a jeweler when you’re shopping for jewelry this holiday season.

Feel free to bookmark this page, print it out, or pin it: just keep it handy as you walk into any jewelry store or visit an online retailer. With the right questions, you can be confident in what you’re buying.

1. What are this diamond’s 4Cs? Can I see an independent grading report?
A jeweler should be able to explain a diamond’s 4Cs in detail and produce an independent diamond grading report to support his explanation. An unbiased diamond grading report, such as the GIA Diamond Dossier®, GIA Diamond Grading Report, or GIA Diamond eReport, ensures that you will know your diamond’s quality and authenticity. For a quick summary of the 4Cs, see part 2 of our 2013 Holiday Buying Guide, 4Cs Tips for Holiday Diamond Jewelry Shopping.

2. Can I see other options in my price range?
Many factors contribute to how a piece of jewelry is priced: the type of gemstone(s) used and it’s quality, the type and quality of the metal in the setting, overall design and craftsmanship, just to name a few. A jeweler should be able to provide you with a variety of choices for any given price point.

3. How do I take care of this piece?
Wearability and care are important considerations. If the piece includes gemstones other than diamond, be sure to find out where they rank on the Mohs scale, which represents gemstone hardness. Ask your jeweler to explain the metal used – some metals are more durable than others. And be sure you know whether the gemstone has been treated, since treated gemstones will require special care. Whether you’re looking for an everyday or special occasion piece, it’s important to understand the care and cleaning tips for any jewelry you purchase.

4. What are your credentials?
You’ll get the best shopping experience from a jeweler who is professionally trained and experienced. Most jewelers are proud to display their professional diplomas from internationally recognized gem and jewelry schools like GIA. In addition, they may be members of trade and business organizations, like the American Gem Society (AGS), Jewelers of America (JA), and your local Chamber of Commerce.

5. What is your return policy?
While everyone wants to give the perfect holiday gift, sometimes the piece just isn’t quite the taste of the recipient. Just in case she was hoping for something different, ask about the return policy. For a significant diamond purchase, like an engagement ring, you might want to also ask about any trade-in programs for a larger diamond down the road.

To avoid holiday crowds, many people opt for online shopping. GIA has a separate set of tips for online shopping that covers online retailers as well as auction sites.

And while GIA doesn’t specifically recommend jewelers, it does offer tools to help you find a jeweler in your area who carries GIA-graded diamonds or have GIA-trained professionals on staff.

Our 2013 Holiday Buying Guide continues next time with an in-depth look at special gemstone cuts and fancy shapes. Prepare to be wowed!

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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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Our exclusive video takes you through the history of the 4Cs, and explains why they remain the universal standard for assessing your diamond. Watch it, and tell us what you think!

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As the creator of the 4Cs and International Diamond Grading System, GIA also established color grading standards and terminology specifically for colored diamonds, based on the color’s hue, tone, and saturation. Today, we identify some of the defining characteristics that help make fancy-color diamonds a true feast for the eyes.

Brown diamonds

As one of the most popular gems to make the trend scene, brown diamonds summon images of luxury and pleasure with trade names like champagne”, “chocolate”, and “cognac”. The cause of color in natural-color brown diamonds is still the subject of scientific investigations. It has been proposed that the color is caused by internal parallel grain lines in the diamond or from color centers.  A color center is an atomic-level lattice defect, found in a diamond’s crystal structure, that can selectively absorb light in the visible region of the spectrum.

Yellow diamonds

Yellow diamonds contain trace elements of nitrogen, and are  also abundant.. Highly saturated yellow stones are considered to be the most desirable color. You will sometimes hear yellow diamonds referred to as “canary,” though this is not an accepted term used in grading yellow diamonds.

Pink diamonds

Pink diamonds can range in color  from  very light pink to reddish purple, including pink-purple, orangy red, purplish red, and more. The cause of color in natural-color pink diamonds is still the subject of scientific investigations. It has been proposed that  their color is from graining inside the crystal or from color centers.. This can also produce red diamonds, though they are extremely rare.

Blue diamonds

Also quite rare, blue diamonds are caused by boron impurities in the crystal – the more boron, the deeper the hue. Blue diamonds have traces of grey, so they never approach the deep saturated color of sapphires.

Green diamonds

The color green stems from radiation which displaces atoms from their normal positions in the crystal lattice. This can happen naturally by the effect of nearby radioactive rocks or when man exposes diamonds to radiation in a laboratory. The green color is usually confined to the surface, not through the entire stone. Natural green diamonds are very rare, low in saturation and somewhat greyish or brownish.

GIA has the ability to determine whether color is natural or the result of an artificial process. To learn more about how GIA set the benchmark for colored diamond reports, go here.

Which color happens to catch your fancy?

The post The Timeless Intrigue of Colored Diamonds appeared first on GIA 4Cs Blog.

The traditional diamond growth method was developed in the 1950s. It involves the use of expensive equipment creating very high-pressures and high-temperatures (referred to as HPHT). This process takes about 5 days to grow a 1-carat crystal that, due to the unique laboratory growth conditions, forms a very distinctive shape. The most common colors for these synthetic diamonds are yellow and brownish yellow, though others such as blue, pink, red and green are also possible.

But over the past decade, a new method for growing diamonds has emerged: chemical vapor deposition, or CVD. Instead of using high-pressure machines, diamond crystals grow from a gas at very low pressures in a vacuum chamber. Only a few companies have the skill to use this process, and most diamond crystals are less than .5 carats and form a tabular  shape, which differs from that of natural diamonds. In contrast to the older HPHT method, this method can grow colorless crystals, while making colors such as blue, yellow, pink, red and green possible as well.

[Note: in both processes, blue is due to the presence of boron in the diamond, while the other colors are the result of a post-growth treatment process involving radiation exposure and sometimes heating]

As synthetic diamond production continues to rise, it’s becoming an even greater necessity to know exactly what you’re buying. To properly identify the differences between a synthetic diamond and a natural one, be sure to receive a professional lab evaluation.

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Many people know that diamonds typically come in a range of colors from D to Z on the GIA color-grading scale.  However, most people don’t know how the naked eye sees color in a diamond.

Diamond Color – D to Z

When visible white light enters a diamond, the gem absorbs some of the wavelengths, while transmitting wavelengths to the viewer’s eye. This process is called selective absorption, and it determines the color of any material, including diamonds.

If little or no color is absorbed by an object, then it appears colorless or white. If the entire spectrum of colors is absorbed, the object will appear black, with an infinite number of possibilities in between.

In other words, selective absorption is the very process that determines the color of your diamond. In diamonds, the presence of nitrogen atoms (or other atoms of impurity) determines the level of absorption, and therefore the color of the diamond. A dog, because its eye processes wavelengths differently than a human, would see a completely different color in the diamond than you would.

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GIA’s 4Cs Q&A series wraps up with some bonus information on fluorescence, while passing along a few friendly words of advice.

Fluorescence

Q: What impact does fluorescence have on the appearance of a diamond?

A: GIA studies show that, for the overwhelming majority of diamonds, the strength of fluorescence has no widely noticeable effect on appearance. In many instances, observers prefer the appearance of diamonds that have medium to strong fluorescence. In rare cases, some diamonds with extremely strong fluorescence may appear hazy or oily; fewer than 0.2% of the fluorescent diamonds submitted to GIA exhibit this effect.

Q: Does fluorescence compromise the structural integrity of the diamond?

A: No. A diamond that fluoresces has the same integrity as one with no reaction to UV. Submicroscopic substitutions and/or shifts in the diamond structure can cause fluorescence as well as prevent it. Nothing in either instance inherently weakens or is bad for the diamond.

Diamond Fluorescence

More about diamonds Q&A

Q: How can you know whether your diamond has been treated or enhanced?

A: GIA issues reports for diamonds that have been laser drilled or HPHT processed, prominently disclosing these treatments on the report. As a further precaution, GIA also laser-inscribes the girdles of diamonds it identifies to be HPHT processed. GIA does not issue grading reports for any diamond that has undergone a treatment process that’s considered nonpermanent or unstable, such as coating or fracture filling.

Q: How do you know if your diamond is synthetic or not?

A: GIA tests every diamond to determine if it is natural. If a diamond is found to be laboratory-grown, GIA issues a Synthetic Diamond Grading Report, which looks distinctly different from the standard grading report. GIA also laser-inscribes the diamond’s girdle with a report number and a statement that the diamond has been laboratory-grown.

Q: How do you know that your diamond is natural and not a diamond simulant?

A: GIA tests every stone to verify that it is, in fact, a diamond. GIA does not issue grading reports for simulants.

For an overview on fluorescence, read “Understanding Diamond Fluorescence“. For more information on diamonds, 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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GIA’s 4Cs Q&A series continues with a careful consideration of carat weight.

Q: What is the difference between carat and karat?

A: Karat (abbreviated “K” or “Kt”) is a unit of measure that describes the purity–or fineness–of gold.

Q: How did the carat system start?

A: The modern carat system started with the carob seed. Early gem traders used the small, uniform seeds as counterweights in their balance scales. The carat is the same gram weight in every corner of the world.

Q: What are “magic sizes”?

A: Some weights are considered “magic sizes”–half carat, three-quarter carat, and carat. Visually, there’s little difference between a 0.99 carat diamond and one that weighs a full carat. But the price differences between the two can be significant.

Q: How is diamond carat weight measured?

A: To determine carat weight, the grader weighs the diamond using an extremely accurate electronic micro-balance that captures the weight to the precise fifth decimal place (the nearest ten-thousandth of a carat).

To see if your knowledge of carat weight measures up, please check out 4Cs of Diamond Quality 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

All diamond images and diagrams are for reference only and may not reflect true diamond carat weight.

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