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GCAL COLOR GRADING


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GCAL COLOR GRADING

The State of Diamond Color Grading

Color grading has become the most controversial process in diamond grading. There are numerous reasons, not to mention that most jewelers and appraisers do not own Master Diamonds or do not have confidence in the procedures they routinely use. Many laboratories are under great pressure to over grade customers’ diamonds. Whether from pressure or internal problems, most of the grading degradation we have witnessed from most labs has been inflated color grades well beyond borderline calls. Another issue has to do with the light source most of us use, or what is contained in the bulbs. For decades, GIA has sold a “Diamondlite Color Grading Box” and furnished bulbs with a degree of UV in them. You can guess what happens to diamonds that are fluorescent. They actually will mask a certain amount of color in the diamond, depending on the strength of fluorescence, and the inherent color of the stone. We understand GIA no longer sells that light box. There are industry wide discounts for diamonds with varying degrees of fluorescence. These are printed at the bottom of the pricing grids beginning on page 7 if you are a subscriber to Palmieri’s Market Monitor, or see the section below on fluorescence. For anyone interested in knowing the true color grade of a fluorescent diamond, there is a UV polycarbonate plastic filter that can be placed under the bulbs when grading for color. Dazor, a lighting company out of St. Louis, MO, has implemented an annual photometric certification program for proper and consistent illumination. Dazor also produces a state of the art lighted viewing cabinet.

Color Grading Procedure

• Use a Precision Master Set of diamonds, with each master being the highest of each grade
• Arrange master set highest to lowest; left to right
• Unknown diamond must be lighter than the master to be a better color than the master
• Start by comparing the unknown to a lower color master and work your way to higher color masters (right to left) until the unknown is no longer lighter than a master stone
• Position the unknown to the right of each master for consistent results
• Comparing the unknown in between two masters is not recommended

Color Grading Tips

• When comparing an unknown to the master try not to just look at each stone separately, try to look at them both as one, as if you are looking just past them
• Don’t confuse darkness for color, especially in fancy shapes. Remember you are grading the amount of color (the saturation) and not the tone (lightness/darkness)
• Brown diamonds of any range are very difficult. Give them, and your eyes, more time to adjust to the light
• It is difficult to see the true body color of diamonds with black inclusions. Try the viewing these diamonds in the ‘umbrella’ position
• Do not check UV fluorescence before color grading
• Magnifying eyewear is extremely helpful and is necessary if the diamonds appear a little blurry

Table Down, Face Up, or Umbrella Position?

• Rounds are always viewed table down, never face-up
• Fancy shapes are viewed table down and angled between point and side so the overall color can be seen
• Fancy shapes can also be viewed face up if the table down view is J color or lower. If the face up view is two colors lower than the face down view, the final color grade will be one color lower than the face down view
• Umbrella view (positioned on side with culet toward grader - see website for additional photos) is very helpful to check and verify a grade decision for fancy shapes, highly included diamonds or those with dark inclusions, and brownish colors
• Always view the Master diamond in the same position as the unknown diamond


 Video: Watch How Diamonds are Color Graded at GCAL


FREQUENTLY ASKED QUESTIONS

I thought diamonds had no color. What does Color mean?

Even though diamonds are considered as colorless, most are shades of light yellow and brown. A diamond with no color at all is extremely rare and ranks as the highest color grade.

Diamonds are color graded on a scale from D (totally colorless) to Z (conspicuously yellowish or brownish). Color saturation gradually increases with each letter grade. Anything more than the 'Z' grade is considered a Fancy Colored diamond. Diamonds are found naturally in every color of the rainbow.

How are diamonds color graded?

Color grading involves determining how little or how much body color is in a diamond. The less body color, the higher the grade; the more body color, the lower the grade. This process has nothing to do with identifying hue, everything to do with deciding the amount— or, more accurately, the lack-of it.

Diamonds are assigned one of 23 possible rankings from D (colorless) to Z (light yellowish or brownish). Using pre-graded comparison stones, known as Masters, gemologists find the closest color match from among the Masters to the stone being graded. These Master Color Comparison Diamonds become the graders standard reference for proper analysis.

A gemologist begins by placing the diamond being graded to the left of the Master Set to get a general idea of the color. Then they move the diamond to the right of the Master-diamond that is a bit more saturated than the diamond being graded. The grader continues to compare the diamond to the known Color Master diamonds until they determine the exact color. The difference between each color grade is very slight, but with experience, experts are able to consistently determine the accurate color grade of each diamond.

Because color grading is a quantity call, the diamonds are studied in the face-down (or bottom-up) position. This means that graders view the diamond's pavilion and culet rather than its table or crown. Why? To eliminate interfering brilliance and glare coming from the diamond's top.

Why does the color scale start at the letter D?

If you're wondering why the scale starts at 'D' rather than 'A,' it's because it was common to sell diamonds as Triple A when the scale was introduced in 1953. To avoid any similarities with prior ratings that were arbitrary and inflated, the jewelry industry adopted a color scale from D to Z.

How do I know my diamond was graded correctly?

Make sure your diamond comes with a Grading certificate from a respected gemological laboratory, such as GCAL. GCAL is an independent laboratory, not affiliated with any jewelers, and has the consumers' best interests in mind.

Before GCAL gives a diamond its color grade, it is individually examined by two experts and verified by a third senior expert. GCAL's laboratory is a controlled environment, equipped with state-of-the-art instrumentation and lighting. There are only a handful of gemological laboratories in the world so well equipped.

In addition, GCAL uses only Precision Master Color diamonds for color grading comparison. Every diamond in each Precision Master Color set is specially selected because it is precisely the right color. GCAL examines thousands of diamonds to compile just one Precision Master Color set.

Although grading diamonds is an expert opinion and not an exact science, maintaining meticulous gemological tools, such as Precision Master Color sets, is one way that GCAL ensures the most accurate, objective and consistent grading possible.

And don't forget... GCAL is the only diamond grading company to stand behind their grading with a money-backed grading guarantee.

Will my diamond change color as it ages?

No. The color of a diamond is stable and permanent. You can leave your diamond in the sun or boil it in cleaner – it will not change color.

The color of diamonds can only be changed by advanced methods such as exposure to intense radiation energy or heating to extreme temperatures, such as 2000°C, while under tremendous pressure. These methods, known as treatments, are used on purpose to change or enhance the color of diamonds. If your diamond has undergone one of these treatments, then it must be disclosed by the jeweler and will be stated on your GCAL certificate.

Does the metal I choose for a ring affect the diamond's appearance?

Yes. Diamonds graded between 'D' to 'H' color look best when set in white metals such as platinum, palladium or white gold. Diamonds with more color, graded 'I-J' and lower, are best complimented by a yellow gold setting.

What causes the different colors of diamonds?

In theory, a diamond is pure carbon with a perfect atomic structure, but in the real world, this is extremely rare. On the atomic level, every diamond has some imperfections such as misaligned structure or, very commonly, impurities such as nitrogen and hydrogen. Nitrogen impurities cause yellow colors, boron impurities cause blue colors and structural imperfections cause pink and brown colors.

What is the difference between a fancy yellow diamond and a 'bad' regular diamond?

The letter diamond color scale ends with 'Z', but color saturation doesn't stop at 'Z'; colors continue to increase in color and are considered Fancy Colored. Fancy Colored diamonds are graded on a broader scale that starts with 'Fancy Light', then just 'Fancy', then 'Fancy Intense' and lastly, the very rare 'Fancy Vivid'. We don't consider any diamond to be a 'bad' color, however, more common colors are the least costly and rare colors are the most costly. To understand how price relates to color grades, think of the entire color scale, from 'D' to 'Fancy Vivid' as a bell curve. The rarest and most costly diamonds – completely colorless and brightly colored – are at each end, and the more common slightly tinged diamonds – 'O' to 'S' – are in the middle.

D, E, F, G, H, I, J, K, L, M... Where to start when shopping?

When considering what color diamond is right for you, start by looking at an H or I color diamond. This is in the middle of the popular color grade range (from D to M color). If you see some color then consider buying a diamond of a higher color grade, and if you don't see any color then consider buying a diamond of a lower color grade.

It is difficult for an untrained eye to see the difference between each individual letter grade, but most people can easily see the distinction between diamonds of a few grade differences, such an E and an H or an H and a K, especially when compared side by side. Color differences are most noticeable when diamonds are next to one another. Keep this in mind when purchasing loose diamonds that will be set next to one another in a piece of jewelry. Make sure they are similar colors – not more than 2-3 grades different.

How does color affect value?

The price difference between each color grade (all else being equal) ranges from about 3% to more than 25%. The price increments increase when the other quality factors are higher. For example, the difference between each color grade for a 1.00 carat VS1 clarity diamond is about 10-15% per color grade, whereas the difference between each color grade for a 1.00 carat SI2 clarity diamond is about 3-7% per color.

Color is more noticeable in larger diamonds and in diamonds with fewer facets such as Emerald and Asscher cuts and, color is less noticeable in well cut diamonds and in diamonds with more facets such as Round and Princess cuts.


FLUORESCENCE

What is fluorescence?

When exposed to ultraviolet light (UV) some objects glow or emit light. Fluorescence in diamonds is caused by submicroscopic features in the atomic structure. Diamonds can fluoresce a variety of colors, but blue is the most common and the most desirable.

How is fluorescence described?

Diamonds emit varying degrees of fluorescence, which is noted on GCAL certificates as None, Faint, Medium, Strong, or Very Strong. GCAL includes the diamond’s fluorescence on the certificate because it is a permanent identifying characteristic.

GCAL uses a set of Master Fluorescent diamonds for comparison to consistently and accurately describe the strength of fluorescence.

How does fluorescence affect value?

Fluorescent diamonds are slightly to heavily discounted in the trade, and that lower price should be passed on to the consumer. Below is a chart showing the approximate percentage of discount based upon size, quality, and strength of fluorescence.


 Video: Watch How Diamond Fluorescence is Examined at GCAL


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