Complete Guide To Colored Diamonds November 20, 2018 – Posted in: Jewelry Blog
In the jewelry business, we spend so long talking about the need for the 4Cs of diamond classification, that it’s easy to forget sometimes that the Color of those Cs is actually a lot more flexible than you might imagine. Enter the Colored diamonds.
The ideal diamond color is usually seen as being “white” which, of course, means colorless in jewelry terms. But diamonds actually come in a wide variety of colors and shades. Even diamonds we class as white, often aren’t. Many will have the barest hint of color, although it is usually extremely difficult to pick up with the naked eye in inconsistent lighting conditions. A completely colorless white diamond is a pure diamond, by classification, and the purer it is, the whiter it is considered to be. So do we just dismiss any non-white stones as oddities or simple curiosities? Well, no, of course, we don’t. Experience tells us that stones considered “imperfect” for the purposes of classification and description can be spectacular in their own right. Non-white diamonds deserve their place in quality engagement rings just as much as their purer brethren.
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Understanding the Diamond Colors?
As expected, the vast majority of diamond engagement rings contain stones that are white. It is these which we instantly imagine when we talk about engagement rings generally. But the impurities that find their way into diamonds can result in anything from brown and yellow – caused by the inclusion of nitrogen, to blue – caused by Boron. Red, pink, green, purple and even black diamonds occur, each of which does so due to a unique combination of impurities and deformation.
Technically, only diamonds ranging from white to light-yellow are classified using the standard GIA classification. More extreme shades of yellow or other colors are classified within a different grading scale. These other colored stones have the name fancy colored diamonds so as to distinguish them from the “purer” end of the scale. Some are much rarer than even a completely colorless diamond and cost much more as well.
To distinguish these white-with-color diamonds from true yellow diamonds, we use different terms. We call these yellow diamonds, and all other colors actually, “fancy” diamonds. Despite the long-held preference for white diamonds, colored diamonds are actually much rarer. In the early days of commercial diamond mining, many colored diamonds may have been discarded for a lack of understanding. It may even be the case that it wasn’t realized that they were diamonds at all. Whatever the reasons, we now know that fancy colored diamonds are now a very popular choice.
Why Different Diamond Colors Occur
The different colors of diamonds are a result of one of three things. For yellow, blue or brown diamonds, the cause of the color is down to light absorption by one or more trace elements present. These impurities will absorb light in specific parts of the spectrum, reflecting the remaining light as a color other than white.
For red or pink diamonds, it is deformities within the crystal structure which causes light absorption. In this case, only light in the red part of the spectrum is reflected in such instances. Uniquely, it is irradiation during the crystal forming process which causes the green color. Some other gemstones created in this way can have their color improved by subjecting them to more radiation, but green diamonds do not undergo this process.
Grading Colored Diamonds
Actually, apart from the D to Z color chart used for white diamonds, colored diamonds are graded in exactly the same way as any other. Clarity, cut and carat weight is all part of the same grading process and GIA standards as white diamonds.
The difference in the grading process is that color is the primary factor for deciding the value. For white diamonds, color, clarity, and cut have broadly equal importance. With colored diamonds, the intensity and purity of the color is king. Clarity and cut are still important, but a diamond with good color and average clarity and cut is often more valuable than one with excellent clarity and cut, but average color.
Many white diamonds have a hint of color, and that color is almost always yellow. On the color scale, which runs from D to Z, anything from D to J color qualifies as colorless or near-colorless. In effect, what this means is that the naked eye will see a white diamond, and not be able to detect the color which may be present. The next grouping is from K color to M. These have a faint color which is visible to the eye, and will usually be the lowest color grade available to buy. Beyond M color are not desirable to most people, and rarely appear in jewelry store displays. It is important to note that these, even at Z color are not yet true yellow diamonds. They are merely white diamonds with some yellow color. It is an important distinction that probably needs some clarification.
The presence of nitrogen creates the yellow color during the formation of the diamond crystal. Nitrogen, although making up 78% of the earth’s atmosphere, is not naturally abundant in the earth’s crust. To find its way into the diamond crystals, it must first undergo plant synthesis. Animals eat the plants, and the nitrogen and, finally, returns to the earth naturally. This process makes nitrogen the most common trace element in diamond crystals. If enough nitrogen is present, we get fancy yellow diamonds. The best stones will contain only nitrogen. Other elements will affect the purity of the yellow color, and this will reduce the value of the diamond.
The highest quality fancy yellow diamonds, often called Canary diamonds will fetch a similar price to the best D color white diamonds. However, many examples are much more affordable if they contain any hint other colors in the yellow.
Blue diamonds are unique amongst all diamonds, in that they are the only ones capable of conducting electricity. Both the color and semiconductor properties of blue diamonds occur because of the presence of boron. As with all colored diamonds, the purity of the blue is the biggest factor when determining value. However, within what are acceptable blue tones, blue-grey and blue-green colors are common. The more blue, the better, but pure blue diamonds are so rare that sub-colors remain very valuable and very popular.
No known blue diamonds exist which achieve the F (*Flawless) grade. Several blue diamonds, though, are Internally Flawless (IF). It is unclear why flawless blue diamonds appear not to exist. Microscopic deformities likely appear due to the boron traces reacting to heat at a slower rate than the rest of the diamond crystal lattice.
In something of an anomaly when valuing colored diamonds, purity of color doesn’t always indicate a higher value for a blue diamond. A deep blue-grey diamond, for example, will cost more than a pure, but pale, blue color. It is the depth of color which contributes to the value of a blue diamond, rather than the purity.
The universe is full of radiation. Usually, though, it is at levels which pose no threat to us. Occasionally, though, a combination of factors conspire to create hot pockets of radiation, including in the earth’s crust. If diamond crystals are growing at the time, the radiation causes a green color to appear.
Large green diamonds are so rare – second only to red diamonds – that the largest fancy, or vivid, one ever sold at auction was only 5.03 carats in weight. The selling price gave a per carat value to the diamond of $3.3m. This is a record per carat auction price for any colored diamond. Larger green diamonds do exist but have a color which has other tones present, or which is paler than the desired vivid shade.
Very few quality green diamonds of notable size ever make it as far as a sale room. They are strictly a collector’s item and are not an investment in the way other rare diamonds might be.
Red and Pink Diamonds
In contrary to other colored diamonds, red and pink diamonds are not simply different shades of the same diamond color. Red diamonds qualify by being a very specific shade. Anything else is either a red diamond with a secondary color or a pink diamond. Red diamonds are formed by atoms in the crystal becoming shifted under the extreme pressures present during the formation. These atoms cause flaws in the structure which causes the absorption of all light except red. Another result of this deformation is that red diamond occurs almost exclusively in VS1 or VS2 clarity only. The clarity makes no difference to the value of a red diamond, as the color is the sole factor to determine value.
Red diamonds are so rare that, for a 30 year period from 1957 to 1987, GIA did not grade a single red diamond. Almost all that do exist are under 1 carat, with the largest red diamond ever found being just 5.11 carats. This makes red diamonds the most expensive in the world.
Pink diamonds, although extremely rare, are more common than red diamonds. They are formed in the same way as red diamonds, but it is unclear as to why some result in a pink color and some red. Red diamonds only ever appear in the same location as pink diamonds, but pink stones occur in much larger weights. Pink diamonds also occur at higher clarity grades than their red counterparts. Several pink diamonds are Internally Flawless, with one – the 59.60 carats Pink Star – being flawless.
In contrast to the largest ever red diamond weighing just over 5 carats, rough pink diamonds can weigh over 400 carats.
Purple diamonds are essentially a red diamond that contains unusually high traces of hydrogen. The deformation which happens in red and pink diamonds also occurs in purple. Although also very rare, purple diamonds do not attract the same value as red or pink diamonds. Part of this is because of the very large number of shades which appear. Both the deformation of the crystal and the level of hydrogen particles affect the purple color. This makes the resulting color of the polished diamond unpredictable, even within crystals from the same location.
Purple diamonds can be treated to improve the color. Such diamonds have a much lower value than natural purple diamonds, but the treatments are often undetectable. This adds an element of suspicion to genuine, natural purple diamonds which come up for sale. The largest purple diamond is around 7 carats, but little is known about it, other than it originated in Russia.
A black diamond is actually a white diamond. Every flaw or inclusion in a white diamond will affect the resulting clarity grade. The more flaws, basically, the less sparkle the diamond has. Black diamonds are white diamonds containing an excess of internal flaws. There are rarely trace elements which produce the black color, it is simply a case of the light which enters the diamond doesn’t get out again. This leads to the perception that the stone is black when it is not.
Black diamonds, effectively, are extremely poor clarity white diamonds. As a result, they do not carry a high value, even when occurring in large sizes. There is something of a niche – but growing – market for black diamonds, because of their unusual appearance, but they are not generally commercially viable. They came to the attention of buyers when Carrie received a black diamond engagement ring in the second “Sex In The City” movie.
Notable Colored Diamonds
The largest red diamond ever is the 5.11-carat Moussaieff Red Diamond. Incredibly, it was discovered by a farmer, in a Brazilian river bed and the rough stone weighed just over 13 carats. The current estimated value of the diamond is in excess of $20m.
The Daria-i-Noor diamond weighs an estimated 182-carats and is the largest pink diamond in the world. From the same 400-carat rough stone came the 60-carat Noor-ol-Ain diamond. Both originated in India, but now are part of the Iranian Crown Jewels.
There are far more lab-grown green diamonds than natural. The largest green diamond is the Dresden Green. It weighs 41 carats and is on display in Dresden Castle. The Dresden Green diamond is the benchmark for the color of green diamonds.
The French Blue diamond was the largest cut blue diamond ever. We’ll never know, unfortunately, as it disappeared during the French Revolution. However, the Hope Diamond, one of the most famous diamonds in history, is almost certainly the French blue re-cut. The Hope diamond sports a long history of misfortune, and the curse passes to any wearer from that moment onwards. Superstitions aside, the Hope diamond has grasped its place in history with both hands.
Many very large yellow diamonds remain uncut, in their original rough state. One is in the Kremlin in Moscow, owned by the Russian government. One of the largest cut yellow diamonds is the Tiffany Yellow Diamond. The stone is on display in Tiffany & Co. in New York, and weighs 128.54 carats. Its original rough weight was 280 carats.
Vintage Colored Diamond Rings
The Bowen ring is a very rare fancy light-yellow diamond ring in an elongated emerald cut. The GIA certified 1.68ct yellow diamond is flanked by two shield cut diamonds weighing 0.70ct. The setting is a combination of 18K yellow and 18K white gold.
The Linas Ring has a 0.60ct colored diamond, certified by GIA as “Fancy brown, purplish, pink”. The setting is yellow gold with a platinum top supporting the bezel set colored diamond. A cluster of old mine cut diamonds makes up the setting.
The Le Marais Ring has a GIA certified, 1.66ct, Brown-Pink Even fancy colored diamond with SI2 clarity in a platinum setting. The bezel itself is 18K yellow gold. A halo of diamonds surrounds the center stone.