Colorless diamonds are rare enough, but naturally occurring fancy colored diamonds are rarer still, which explains why they often command the highest prices at auction. Diamonds can come in all sorts of colors, from vivid blues to fiery oranges, but how do they get these spectacular colors in the first place?
Fancy colored diamonds ('fancy' denotes that the diamond acquired its color naturally, rather than being artificially treated) occur in nature for several reasons. Color refers to the natural body color of a diamond and not to the reflection of spectral colors that flash when a diamond moves. A colorless diamond is made of 100% carbon. When another natural trace element gets into the carbon chain, it can add a color. What's more, different elements can cause a diamond to take on different colors, creating an assortment of stunning fancy color diamonds! For instance, nitrogen causes yellow, brown and pink hues, while boron produces blue or blue-grey. Hydrogen can cause diamonds to become red, violet, blue or green.
Another way for the stones to acquire color is via unusually intense pressure or heat during the compression stage that gives birth to diamonds: this can lead to red, pink or purple diamonds. Naturally occurring radiation can also affect the color, making diamonds blues or green, mines in certain parts of the world have a greater chance of unearthing these.
All diamonds aim to come out as, pure 100% carbon and colorless as possible. But as they are being created under these extreme amounts of heat and pressure, plus sometimes natural trace elements get into the carbon chain and naturally occurring radiation can all add color and inclusions & blemishes into the mix. Hence, as diamonds are forming, they often at times interact with these things which causes the structure and the color of the stone to change.
Gemologists tend to refer to these color changes as 'defects'. So, are all diamonds created equal? In a word, no. The amount of color in the diamond will depend on how much these things has managed to interact with the diamond which will actually affect the hue, saturation and tone of the diamond color. Let's break it down together, starting with 'hue'.
Put simply, hue is just the shade of color a diamond can have. You can get different colored fancy diamonds, with different hues like red, blue, green, purple etc., but colorless diamonds can have hues too! For instance, the diamonds that you see in your local jewellery store will all have a certain hue to them, even if they appear mostly colorless. As you move along down the color scale for diamonds, more hue is visible. In most cases this hue tends to be yellowish, and that is reflected in the 'Diamond color scale' shown below. Colorless grades are determined by comparison to a master set. Each grade represents a step on the color scale and is a measure of how noticeable the color is. In colorless diamonds, the full scale goes from D all the way to Z.
What is super important to know however, is that yellow is NOT the only hue a diamond can have! Now remember, we are not really talking about fancy colored diamonds here (like vivid pinks and blues), but rather colorless diamonds with a hint of color to them (but in no way could be classified as colored diamonds). So, these colorless diamonds can have four different basic hues; yellow, brown, green and gray:
If you want to buy a diamond that is as close to colorless as possible, you want as little hue (of any type, be it yellow, brown, green or gray) as is financially viable for you (knowing that the less color in the diamond the higher the ticket price). If you were buying a colored diamond (like a bright yellow or pink) then the opposite would be true; you would want as much hue in that diamond as you could possibly afford! The less color a diamond exhibits, the higher the rarity, and therefore the higher the value.
The saturation of a diamond's color basically refers to the intensity of the hue color found in the diamond. Think of it this way: If a few drops of blue food coloring is added into a glass of water which is only filled 1/3 of the way, the water will turn blue. Now if more water is added to the glass, the base color will remain the same (i.e. blue from the dye), but the concentration of that color will diminish as water is added. The less water, the more concentrated the hue, the more water, the more diluted the hue.
Tone just refers to how light or dark the diamond appears. Let's go back to our glass of blue water and imagine that you mixed a bit of black food coloring in there with the blue. The hue would still be blue (the original color), the saturation would stay the same (how diluted/concentrated that hue is), but the water would now be darker in tone.
As you can from the image below, for yellow hue, the lighter the tone and the lower the saturation, the fainter the color found in the diamond. By contrast then, the darker the tone and the higher the saturation, the deeper and more vivid the color will be in the diamond. In fact, the deeper and more vivid the color gets, the more it moves out of the 'colorless diamond with a hint of color' realm, and in to the 'fancy colored' diamond realm.
What is important to see here though is that the yellow diamonds sitting in between the 'faint', 'very light' and 'light' color band are not considered to be 'fancy' colored diamonds, even though they show a fair amount of color (i.e. they have a distinct hue and a little bit of saturation/tone). They only qualify as 'fancy' once they have a certain amount of saturation and tone in them.
Diamonds with less color allow more light to pass, releasing more brilliance and fire. A diamond acts as a prism by dividing light into a spectrum of colors and reflecting this light as colorful flashes called dispersion or fire. Similar to looking through colored glass, color in a diamond will diminish the spectrum of color, or fire, emitted by acting as a filter. A diamond with a higher color grade, i.e., one with less color, demonstrates more colorful fire.
Generally, the less color a diamond has, the more valuable it is. Natural diamonds have a wide range of colors ranging from completely colorless to colored diamonds that come in concentrated colors like pink, yellow, and blue, but are graded on a different scaling system.
The color grading system for natural colorless diamonds uses the letters of the alphabet from D through Z. D represents the least color, and is therefore the rarest and most valuable grade. Z grades have the most color within a normal range and are the least expensive. It is hard for the unaided eye to see variations in color grades D through J unless the stones are observed side by side.
Diamonds should be color-graded under exacting conditions by an expert grader. Using specially filtered cool, white light, these graders compare sets of diamonds with known colors, graded by the Gemological Institute of America (GIA) against their master set. To obtain the most accurate color grade, graders usually place diamonds on their sides or upside-down against a neutral background, to help decrease the play of spectral colors that diamonds reflect.
Very Light Yellow
Completely colorless diamonds (such as D and E) are much rarer than others which is why they come with a higher pricing premium. The key question is always where to draw the line when choosing the color of a diamond - how far can you compromise color before the diamond is too tinted? The answer to this question is relative to your budget and quality expectations.
D is the highest color grade attributed to a diamond, denoting that the stone is completely colorless (white); as such, they are extremely rare and command the highest prices. When looking at a diamond with the naked eye, E and F colors can also look similar to the D color diamond. A D color diamond looks best when set in white gold and platinum, as the white color of the metal further highlights the colorless quality. However, D color diamonds can also look beautiful in rose and yellow gold. Yellow gold reflects color and some color from the setting will come through the stone, negating the diamond's colorless effect.
An E color diamond is visually stunning and has very high color purity. It is incredibly rare and has almost no recognizable color shading. To the naked eye and even under 10X magnification, an E color diamond will not show any tinges of yellow color. The color difference between a D and an E graded stone is usually only visible to an expert gemmologist using master stones as a comparison, 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, although E graded stones are slightly cheaper.
An F color diamond has excellent beauty and contains a minute shade of color that is undetectable by the untrained eye. It is also very rare and considered to have high color purity. When looking for a diamond that will not exhibit shades of yellow to the naked eye, the F color certainly fits the bill and can be more affordable than a D or E color diamond. The color difference between an E and an F is only visible to an expert gemmologist using master stones as a comparison, 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. F grades are the lowest and therefore least expensive of the premium colors.
A G color diamond is exquisite and has minor traces of color that can be identified only by diamond professional. It is also the most popular diamond color and provides a great blend of beauty and value. G stones appear colorless especially once set and therefore offer excellent value for money. A platinum or white gold setting can work to hide traces of yellow color in the diamond, however a G color diamond is versatile and can look great with rose and yellow gold.
H colored diamonds are near colorless diamonds which still appear totally white or colorless if they are not compared side by side with higher color graded stones. The H color is generally considered the watershed between colorless diamonds and slightly tinted diamonds. An H color diamond has gorgeous appeal as its slightly identifiable shade of color does not affect the diamond's brilliance. It is one of the most popular colors because of its visual attractiveness and value. An H color is a good balance between these factors and can be a great choice if you're trying to maximize for other characteristics like carat or clarity.
I colored diamonds are very slightly tinted diamonds, however, once set in jewellery, these stones may appear colorless. An I color diamond delivers excellent brilliance even as some shading of color can be identified by a gemologist. The color is still not recognizable to an untrained eye and provides excellent value. Depending on the diamond, an I diamond can be a good choice as the yellow color is not too perceptible. However, it is a good idea to ask a gemologist to help you find a stone that faces up white before making your purchase. If you are looking to maximize your budget, then an I colored diamond offers great value for money.
J colored diamonds are very slightly tinted diamonds, however, once set in jewellery, especially in yellow gold, it is harder to see the slight yellow tint which the J grade produces. A J color diamond has exquisite sparkle and value (as long as you're getting a stone that's cut well, of course). It has a shade of color that is only detectable by trained professionals and allows for a larger size or higher clarity that may be more palatable to your budget. Talk to a gemologist to help you find a stone that faces up white and discuss the diamond shape you're considering, as some amplify the color of your diamond.
K colored diamonds are slightly tinted diamonds, however, once set in jewellery, especially in yellow gold, it is harder to see the slight yellow tint which the K grade produces. A K color diamond is considered a white diamond that does not compromise the stone's sparkle. Some shading of color may reflect in light, but it is still difficult for the untrained eye to identify the color grade. Keep in mind, though, that a K color diamond can look yellow to the naked eye, especially in larger diamond sizes over 1.50 carats.
An L color diamond is scintillating and considered a white diamond that does not distract from the diamond's sparkle. Slight color may be detectable to the untrained eye, especially when viewed from the side. It looks best in yellow gold settings, which minimize contrast between the diamond and the setting. Check with a gemologist before purchasing an L color diamond to ensure that it is the correct color for you.
Diamonds in the N-R color range have an easily seen yellow or brown tint, but are much less expensive than higher grades.
For almost all customers, S-Z diamonds have too much color for a colorless diamond.
Natural fancy yellow diamonds begin where the colorless D-Z grading scale ends.
Lab reports from the Gemological Institute of America (GIA) and the American Gem Society (AGS) do not rate brown or gray hues of a diamond that are J color and above. The hue of these diamonds therefore can only be judged by visual inspection.
Diamonds in the D-Z color ranges with a yellow hue will only have their letter color grade noted on the lab report.
Diamonds in the D-J color ranges with brown or gray hues will only have their letter color grade noted on the lab report.
Diamonds in the K-M color ranges with brown or gray hues will receive a letter color grade with the addition of a "Faint * " hue rating. The syntax on the lab report will be the diamond's letter color grade + "Faint *** " Brown or Gray depending on the hue such as "K, Faint Brown".
Diamonds in the N-R color ranges with brown or gray hues will receive a letter color grade with the addition of a "Very Light * " hue rating. The syntax on the lab report will be the diamond's letter color grade + "Very Light *** " Brown or Gray depending on the hue such as "Q, Very Light Brown".
Diamonds in the S-Z color ranges with brown or gray hue will receive a letter color grade with the addition of a "Light * " hue rating. The syntax on the lab report will be the diamond's letter color grade + "Light *** " Brown or Gray depending on the hue such as "U, Light Brown".
A diamond having a hue other than yellow, brown or gray and having a color grade of G and below will be graded based on the fancy color scale starting with faint such as "Faint Green".
Diamonds below the Z color grade will use the colored diamond color grades and will note any hues if present such as Fancy Brownish Yellow which would denote a Fancy Yellow diamond that has a brownish color modifier.
It is important to note that at times, a diamond having a slight brownish tint in the I,J,K color ranges can appear to face up whiter in natural daylight as opposed to a stone having a pure yellow hue. These types of stones should be considered on a case by case basis. In many instances, diamonds having hues other than yellow are slightly discounted due to their traditional undesirability at the wholesale level. A consumer may prefer a stone with a slight brownish tint therefore and reap a financial benefit in doing so for this reason. We recommend setting stones with a brownish hue in rose gold which can impart an attractive peachy tone.
If a conscious decision is made to purchase a diamond with a gray, brown or greenish hue as a matter of preference, it's worthwhile to consider post purchase factors. Due to the stigma that these diamonds have with diamond traders and jewellers, the future resale value of these diamonds will be handicapped because of their undesirability in the trade. A professional jeweller that is offered a diamond with a hue will either severely under value the diamond or might refuse the transaction. This issue might arise in the future for those wanting to upgrade their diamond.
Consumers not educated in the nuances of hues sometimes unknowingly purchase a diamond having a tint. This is because tinted diamonds are difficult to distinguish without having an un-tinted diamond to compare it to. Experienced gemologists can recognize a brown, green or gray hue in a diamond very quickly though. The sale of tinted diamonds is a common occurrence with diamond retailers acting as drop shippers selling diamonds based strictly on a lab report without additional imagery or videos. Diamond suppliers specifically list their undesirable, tinted diamonds with retailers that sell based on lab reports and not imagery since they are able to sneak in these stones to an unsuspecting or uneducated purchaser. It is important for the consumer therefore, at the minimum, to make their buying decision based on high resolution imagery of their diamond and not strictly based on a lab report which might not note a hue. Comparing numerous diamonds of the same color from the same vendor can help in the recognition of a tinted diamond.
The bottom line here, is that embracing a hue other than yellow, especially gray, can reduce the cost of the diamond (because yellow hue is the most popular and recognizable, therefore the more expensive) without compromising on the beauty of the stone itself. And If you are choosing a diamond that sits in the D-J color bracket, just remember that the hue of those stones will not always be yellow, and that it will not be stated on the diamond grading report.
Diamond color is graded by evaluating the body color of the diamond on a pure white background, face down. Gemologists will compare the diamond to master stones, or a GIA verified set of cubic zirconia, with grade color shading. If the diamond has more yellow than one but less than the other, it will receive a grade in that range. (For example: More yellow than F, but less than G, would be a G color diamond. You might also hear these referred to as "G+ color diamonds" to indicate that they're at the top of this specific color range, or whiter than other stones in the same color grade.)
The picture below shows an approximate guide to 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. Round brilliants are graded table-down up to Z on the color grading scale, but face-up observation increases in importance when we are grading fancy shapes. The face down orientation makes the detection of body color easier because brightness and fire are minimized when the diamond is face down:
Swipe left to see more.
While changes in diamond color are very subtle, pricing changes are not. The price difference between each color grade (all else being equal) ranges from about 8% to more than 25% in the higher colors. For the perfectionist, D through F color diamonds are a great choice. For a more value driven decision, consider an I through K color. It's extremely important to keep in mind that diamonds of all colors show fire and brilliance. Consider all other elements like the full budget for the ring and your preferred metal.
Purchasing a lower-color diamond concedes only small visible differences, but the savings can be very noticeable. The most noticeable cost difference is often from G to F color grades. The all other elements like the full budget for the ring and your preferred most popular color grade is a G, for this reason, with H closely behind.
Metal color can play a role in which diamond color you should select. A lower-color diamond can actually look beautiful (and more white) in a yellow gold setting. That's because a yellow gold setting decreases the contrast between your diamond and the setting. A little yellow tint will appear more yellow by comparison if placed in a white gold setting.
But the color of the metal isn't the only factor here. Additionally, the amount of metal, and the type of setting, can show off more or less of the diamond. Depending on this, you may want to select a lower or higher color on the scale.
Fancy-shaped diamonds (shapes other than round cut) tend to show more color. Pear, oval and marquise cuts exhibit more color near their points and edges. The Princess, emerald, asscher, radiant cut and cushion cuts reflect more color in the body. If you love the look of a G color diamond in a round cut, assume you'd want an F in another diamond shape.
With diamonds of any shape, as the carat weight increases, color can be more obvious. With larger sizes, it's important to choose higher colors. You can also learn about the other factors that affect diamond pricing below.
We ranked the importance of the color grade (1-10: 1 least important, 10 important) as it relates to the shape of the diamond. Shape is a critical element in determining how much color is shown:
|Round||4/10||Their brilliant facets can mask color. Therefore, with this shape you do not have to get an overly high color grade. You can balance color with other factors like cut to get the best value and look.|
|Princess||5/10||The color shows more than rounds due to the depth and size of the body in the diamond.|
|Emerald||6/10||The open, deeper body of the diamond tends to show more color. The larger facets don't allow sparkle to mask color.|
|Asscher||6/10||The open, deeper body of the diamond tends to show more color. The larger facets don't allow sparkle to mask color as well. If gettng a smaller asscher diamond, something that is below 1 carat you may not have to get as high of a color. When purchasing one larger than a carat, pay closer attention to color.|
|Oval||7/10||Elongated shapes, specifically ones with points show less color in the body, but much more near the edges and points. Again if opting to get an oval that is larger than 1 carat, pay closer attention to the color. Look at also how shallow or deep the diamond is. Deeper diamonds will show a little less color.|
|Marquise||8/10||Elongated shapes, like the marquise will show more color along the points. If getting a marquise that is elongated, be sure to look carefully at images and videos of the diamond to understand color.|
|Pear||8/10||Elongated shapes like the pear will show more color in the points of the diamond. Be careful as to how narrow or fat the diamond is. With a more narrow point, color will show easily.|
|Heart||8/10||With a pointed bottom and an edge that curves inward at the top, a larger diamond can show color. However, color showing may not be a large concern with heart shaped diamonds that are smaller than 1.25 carats.|
|Radiant||9/10||Radiant diamonds can show color fairly easily due to the type of faceting. Be sure to consider color when choosing.|
|Cushion||9/10||Cushion diamonds can show more color based on the type of faceting. With a brilliant cut cushion, color showing is less of a concern. However, with one that has larger and more open facets, color can show more easily. Take a close look at your diamond to decide and have a gemologist explain to you which kind of faceting it has.|
One final factor affects a diamond's color: fluorescence. But unlike those diamond myths you may have heard, diamond fluorescence is your friend. Fluorescence is the diamond's reaction to UV light (a.k.a. black light). Fluorescence is caused by naturally occurring trace elements, such as boron, that become part of diamonds as they grow. In very rare instances, it affects the visual properties of diamonds.
It is recommended that in higher colors (colors D-G), fluorescence should be faint or none. Fluorescence can whiten a diamond for those that are on the lower (more yellow) end of the color spectrum. When the diamond is already colorless, although very unlikely, it can give it a whitish, grayish tint. This is typically the case in less than 1% of all diamonds with fluorescence. The more common impact is color improvement in lower colors.
In colors such as I-L, we recommend considering medium or strong fluorescence. It can improve the visibility of a yellowish tint, thereby visually making the color appear a shade whiter. A diamond with fluorescence is also generally cheaper than one without. Especially choose fluorescent diamonds in J, K or L colors, as they also provide excellent purchase value.
With D, E and F diamonds, you can be assured that the diamonds have no trace of color and look crystal clear. With this color range, any metal setting will look great and bring out the sparkle of the diamond. As D and E color diamonds are quite rare and valuable, you will see large price jumps when moving up color grades within that range. Unless you are immensely particular about color, you can safely get an F color diamond. To the naked eye, an F color diamond will look as good as a D or E color diamond with little difference seen, except on the price tag.
For colorless diamonds the differences between D to G are barely visible but can offer 20 to 40% better value. D is generally more for the investor or diamond connoisseur.
While containing traces of color, G-J diamonds are suitable for a platinum or white gold setting, which would normally betray any hint of color in a diamond. G, H, I and J color diamonds are considered colorless by GIA. For most diamond sizes and shapes, they can be a good option. If getting a diamond that's as close to colorless as possible is important to you, stay within the G or H ranges. J and I color diamonds can be good options, but the amount of yellow they display varies based on size, shape and fluorescence. If you're choosing yellow or rose gold, you can move down a color grade. The metal color will make the diamond look slightly whiter.
Because I-J diamonds are more common than the higher grades, they tend to be a great value. An I-J diamond may retail for half the price of a D diamond. Within the G-J range, price tends to increase 10-20% between each diamond grade.
I and J colors will generally face up white from the top, but you will be able to detect slight yellow or brown tints when viewed from multiple angles. We highly recommend staying with GIA only for these color grades, as any other certificate in this range is likely to fall below your color expectations.
Some reputable jewellers currently offer only stones in the higher range of D-J, however, lower color grades may possibly be made available on special request from some them.
For the best balance of value and look, G through J is a great range. This rule applies to most carat weights. However, if you're looking for a diamond above 1 carat, consider staying with G or H. (Remember, that's because color can show more easily as the diamond carat size goes up.) Once set in a ring, the diamond will look equally as good as a higher color diamond. Factor the shape into consideration when deciding on a color range; fancy shapes will show more hue.
Beginning with K diamonds, color (usually a yellow tint) is more easily detected by the naked eye. Set in yellow gold, these warm colored diamonds appeal to some, and are an exceptional value. Others will feel they have too much color. Due to its perceptible color tint, a K diamond is often half the price of a G diamond. Avoid K and L color diamonds for diamonds larger than 1 carat as the color is more noticeable. If color is the least important factor for you, K and L colors can be considered. But you should keep in mind that if you're opting for a setting with a lot of accent diamonds, like pave or halo settings, these smaller stones may make your center diamond look more yellow. You'll see quite a big price drop from higher color ranges, though. This color range can also be an option for those who want a vintage or antique inspired ring.
K and L are acceptable on a GIA certificate in terms of tint if that major compromise is needed to reach size within a budget. We strongly recommend setting these diamonds in Yellow or Rose Gold jewellery to make the diamond appear less tinted.
If you want a larger diamond, don't compromise on the color. Along with cut, color is the most important factor when choosing a diamond. These two factors deeply impact the look and beauty of the diamond.
Color becomes much harder to detect once a stone is set in a ring. 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.
The color of the mounting will affect the diamond's color. Yellow gold makes slight amounts of yellow in a diamond less obvious, while white metal mountings make color more apparent. Rose gold can have a similar effect, but to a lesser degree. Platinum and white gold will make yellow tints most obvious.
A ring setting that covers more of the diamond, like a bezel or channel setting, will hide color. One that showcases more of the diamond, such as a solitaire, will be less useful in hiding any yellow.
Don't fret if a color grade isn't perfect. Most untrained observers (and many gemologists) can't distinguish a color grade from the next unless the diamonds are compared side-by-side in a controlled environment.
Matching smaller accent or side stones with the center diamond is a crucial aspect of making high-quality jewelry. Color is the most important factor in ensuring a match. Larger diamonds tend to show color more easily, so ensure your accent stones are within a couple color grades of your main stone, particularly with halo and three-stone ring settings.
However, don't be too concerned if the grade is not an exact match, as color and inclusions are harder to see in smaller accent diamonds. Try to use G color diamonds for accent stones because you will love the overall look of your ring. These stones match a large range of center stone grades, from D color diamonds to J color diamonds, but you might see some contrast if you choose a stone lower than that.
While colorless diamonds are the most popular, they are just one category of diamonds. The other category of natural stones is known as fancy color diamonds. Although relatively rare, they have been found in every color of the spectrum.
Diamonds that have color beyond the D - Z scale or have other traces of color including the typical yellow or brown are considered fancy colored. (A fancy shaped diamond is any shape other than round.) Fancy colored diamonds are extremely rare. Only one diamond in 10,000 is a color other than yellow or brown. Depending on the hue, saturation (intensity) and tone of a diamond, color can either detract from or enhance its value. Red stones are the most rare and have the greatest value. There are only about 40 to 50 red diamonds in the world. Diamonds are graded by laboratories on a scale with 27 different hues. Popular fancy color brand names include cognac, champagne, chocolate, icy and canary.
Some of the most famous fancy color diamonds include The Hope Diamond (a walnut-sized blue diamond), the Hancock Red (which sold for $926,000 per carat at a 1987 auction), and the Dresden Green (the largest green diamond ever found).
Fancy color diamonds are not graded on the same color scale as "colorless" diamonds. Rather, their value is derived by color intensity that ranges from Light at the lower end to Vivid at the high end. The more intense or strong the color appears, the more valuable the diamond. Color intensity is the most important factor when purchasing a fancy color diamond.
The distinct difference between fancy color diamonds and other colorful gemstones such as rubies, sapphires, and emeralds is in the mineral makeup. In particular, it's the presence of carbon that differentiates fancy color diamonds from other colored gemstones.
All natural color diamonds are graded by gemological laboratories under controlled lighting environments similar to that of natural daylight. Fancy colors are graded by GIA by evaluating the strength of color and the undertones of all colors present. Diamonds can have multiple undertones, with dominant colors such as Fancy Light Orangy Pink or Fancy Yellowish Green. We typically recommend seeing the diamond in person before purchasing due to the importance of hue, tone and saturation. An image or video will rarely accurately capture the diamond's fancy color and brilliance in this particular category. Diamonds are also tested for treatment, synthetic additions or alterations to ensure their authenticity.
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.