Red Diamond Value, Price, and Jewelry Information

Does Red Diamond Make a Good Jewelry Stone?

Red diamonds are just as strong as colorless diamonds. As such, they are unaffected by ordinary exposure to heat, light, and everyday chemicals. The one weakness shared by all varieties of diamond is their propensity to chip if impacted with enough force. As natural red diamonds are so valuable, if you choose to wear one, particularly in a ring, it is advisable to opt for a design that protects vulnerable corners, edges, and points.

Matching Red Diamonds

Matching red diamonds is a virtually impossible task because it requires jewelers to have access to enough gems to find sets. If someone did manage to assemble a number of red gems in one place (a daunting task in its own right), they then would need to find stones that share each of the Four Cs (color, cut, carat, clarity). With luck, some tiny red gems might be similar, but you won't find a match for sizable gems like those listed above.

The History of Red Diamond

For most of the fancy colored diamond varieties, there are historical references describing stones dating back centuries, if not more. Again, red diamonds are different. The first recorded red diamond was the famous Hancock Red which is likely from Brazil. This Fancy Purplish-Red gem was named for the gem collector Warren Hancock who bought it in 1956 for $13,500. Fashioned into a round brilliant-cut gem, the Hancock became an overnight sensation in 1987 when it sold at Christie's for $880,000 despite weighing only 0.95 cts.

It is important to note here that the relatively small size of the Hancock Red is in line with the average size of red crystals found. One source says that, of all diamonds with a primary red color including those with a modifying hue, less than 400 submitted to the GIA weigh more than half a carat.

Red Diamond Color

The discovery of a pure red gem is equivalent to winning the lottery for any mine on a number of fronts. First, diamonds with a red hue are the rarest of any of the fancy-colored diamond varieties. Secondly, the associated values are astronomical so the mine can make a lot of money from them. While diamonds with a blended color grade including purple, brown, and orange hues are more often found, they still are extremely uncommon.

What Causes Red Diamond Color?

As a red hue is so rare, there is still mystery surrounding its causes. However, scientists have made some headway in understanding what makes red diamonds red by examining them alongside pink, purple, and brown gems, all colors that owe their hue to similar coloring agents.

Unlike other fancy colors that are triggered by chemical impurities like boron for blue or nitrogen for yellow, a red or pink color expression is not caused by foreign elements. Rather, red and pink diamonds are colored as the result of lamellar deformation known as "graining." To understand graining, we need to first learn how the carbon diamond crystal is put together on an atomic level. It should be noted here that brown diamonds are also colored by lamellae, but they were exposed to more pressure than red and pink stones. This point emphasizes that only a rare set of conditions allow red diamonds to be created.

Diamond Crystal Structure

In their purest form, diamonds are made solely of carbon atoms that are interlocked in a perfect cubic formation. It takes tremendous heat and pressure to force carbon atoms to bind together in this fashion, but, once it happens, the resulting crystal is extraordinarily resilient. In fact, it is because the carbon atoms are so tightly bound that diamonds are the hardest naturally occurring mineral on Earth, meaning that their surface is virtually un-scratchable by anything except another diamond. Additionally, thanks to the uniformity of this conformation, such pure diamonds allow light to pass through cleanly and are colorless.

That is not to say that diamond crystals are immortal structures. If a mature diamond exists in an environment with extreme heat and pressure, its carbon atoms may be forced to slide along what is called a "glide plane" which usually happens in the direction called the {111} plane or "octahedral" plane. This slippage may not split the stone in two (though it might lead to small internal fractures), rather, it creates a flat plane in the stone where the atoms are slightly displaced. You may hear this referred to as plastic deformation, lamellar dislocation, or graining.

Deformation

These areas of displacement affect how light behaves inside the crystal, causing a red color to be concentrated and expressed. Typically, diamond crystals will have multiple levels of lamellar deformation rather than a single one. Generally speaking, the more layers of graining, the darker the color expression. Let's take a closer look at how this happens.

The first thing to understand is that diamonds are rarely made of pure carbon. More often, the crystal has a number of chemical impurities mixed in, the most common of which is nitrogen. As noted above, red diamonds don't have to include nitrogen to slip under the sheer stress that causes graining. However, the reality is that most mined diamonds have at least some nitrogen atoms interspersed in their crystal lattice. Indeed, approximately 98% of all natural diamonds have some measurable amount of nitrogen present. As nitrogen atoms are a different size than carbon atoms, their presence creates a position of weakness in the crystal. When the sheer stress is high enough to cause dislocation and create a graining pattern, it often does so where these nitrogen atoms are concentrated.

Diamond Types

Because nitrogen is so common, gemologists separate diamonds into two groups: those with nitrogen and those without. Gems with nitrogen are classified as Type I and those without are Type II. As nitrogen makes diamonds more vulnerable to plastic deformation, most red diamonds are Type I. Type I diamonds may be further subdivided based on how their nitrogen atoms are scattered. When nitrogen atoms occur in groups, the diamond is classified as Type Ia. If the individual nitrogen atoms are isolated, the gem is a Type Ib.

Examining Type Ia diamond further, if the gem has centers where nitrogen atoms are paired up, that center is called Type IaA. If, instead, the nitrogen centers are made of four nitrogen atoms surrounding a vacancy where a carbon atom should be, that center is called Type IaB. Diamonds are named Type IaA or Type IaB depending on which nitrogen center type is dominant within the stone.

While diamond crystals may include both Type IaA and Type IaB nitrogen centers in their crystal, the landmark Gems & Gemology study from 2018 referenced above showed that the vast majority of red diamonds they analyzed had more Type IaB centers than Type IaA. Furthermore, the measured amount of nitrogen tended to be in what is considered the low to moderate range (20-100 ppm).

Identifying Red Diamonds

Standard Diamond Characteristics

While issues like fluorescence change with the various fancy colors that diamonds can exhibit, some measurements are universal.

• Using a standard refractometer, diamonds will register as over the limit (OTL).
• Their dispersion which causes the beautiful multicolored fiery flashes that diamonds are known for is 0.044.
• They will not show birefringence (also known as doubling) and are not pleochroic.
• Lastly, their specific gravity (SG) is 3.52 (+/- 0.10).

Absorption Spectrum

One of the most helpful methods of analysis for red diamonds is the examination of its absorption spectrum. Looking at the spectra for red gems show a characteristic band at 550 nm which also is present in pink stones. This broad band absorbs light in the shorter wavelengths while allowing the longer wavelength red hue to be expressed.

Another feature that can sometimes be observed in the spectra of red diamonds is a line at 503.2 nm that is caused by H3 centers. It is believed that H3 centers are created when two nitrogen atoms appear besides a carbon vacancy in a neutral charge state. This may happen naturally but, more often, can also be induced when a diamond is irradiated and then annealed or subjected to high pressure, high temperature (HPHT) annealing. The presence of H3 centers is thought to intensify the red color of a stone.

Fluorescence

The Gems & Gemology study mentioned above analyzed one hundred red diamonds and showed that every gem fluoresced when exposed to longwave UV light. Of this sample, 95 gems glowed a blue color and most had either a medium reaction (53) or weak reaction (30). For context, about 35% of colorless diamonds typically fluoresce a blue color under longwave UV light.

Clarity Features

Red diamonds may contain many of the inclusions that you will observe in colorless diamonds. The most common will be graphite which is unconverted carbon. Thanks to the plastic deformation, small internal fractures may be present. You may also find included crystals of other minerals like garnet, corundum, or diopside.

Considering the extreme rarity of red diamonds, buyers don't really care about their clarity grade. The saying "beggars can't be choosers" comes to mind. Yes, a diamond's clarity will affect its value, especially when there is significant, eye-visible, inclusions, however, this is not a major concern for ultra-rare red diamonds. Take, for example, the Lady in Red discussed below. This gem has a clarity grade of I1, meaning that there are apparent eye-visible clarity characteristics. Yet, it is worth over a million dollars.

Are There Synthetic Red Diamonds?

The same treatments that are applied to natural diamonds to create a red color also work on synthetic gems. Again, treatments usually involved irradiation followed by annealing.

There are two methods that are used to grow diamonds: chemical vapor deposition (CVD) and high pressure/high temperature (HPHT). It has been documented that brown CVD gems may be treated post-growth with annealing and irradiation can become red. While proof of concept has been established here, red CVD diamonds are still rare. Similarly, red HPHT synthetic gems owe their color to irradiation and low-temperature annealing.

Find this Diamond

Red Diamond Enhancements

With red being such a valuable and desirable color, it is not surprising that people have searched for ways to induce or concentrate a red hue in natural stones. Some of the best results come from a multi-step process that involved irradiation, followed by high pressure, high temperature treatment (different from the HPHT growing process) that creates Type IaB nitrogen centers. Finally, the gem undergoes carefully controlled annealing (a regulated process of heating and cooling). Some stones have been found that skip the HPHT step. Fortunately, this type of treatment leaves behind clues which can be identified relatively easily including irregularities in both the infrared and visible absorption spectra.

Other, less sophisticated, methods of creating a red color include coating the gem (which will wear and discolor over time) and fracture-filling gaps inside the diamond with a colored filler.

Where is Red Diamond Found?

Today, there are three primary locations that are known to harbor red diamonds.

The Argyle Mine, Kimberley, Australia

The Australian Argyle Mine was mentioned at the beginning of this guide and it has definitely earned the top spot on this list even though it is no longer active. Located in the Eastern part of the Kimberley region on the Western side of the country, craftsmen diligently fashioned any rough red crystal weighing more than 0.20 ct. into a sparkling faceted gem. These gems were sold at the ultra-exclusive annual Argyle Pink Diamonds Tender.

The reason that so many pink and red diamonds come from this location is because it was the site of extreme temperature and pressure which, as will be described below, is the believed cause of both red and pink colors. In a true partnership, all of Argyle's pure red treasures, numbering less than two dozen over the lifetime of the mine, were submitted to the GIA for official grading before being offered for sale at their tender.

Brazil

Another country that contributes red diamonds to the market is Brazil. Unlike the Argyle which existed on its own and kept meticulous records, there are a number of mines around the Abaeté River that have yielded red gems, but the details regarding the discoveries are not as well documented. These mines are owned by GAR Minerals, a company run by a fourth-generation diamond mining family, and they are expected to continue operations for at least another two generations. Hopefully, we will see a handful of new red diamonds from this location in the coming years.

South Africa

Considering that many millions of carats of diamonds are mined every year in Africa, it should not be surprising that some reds have come up in the mix. In particular, South Africa has produced a few impressive red diamonds.

Other Sources

Some other countries including Russia and India have yielded a handful of red diamonds, but these are isolated findings.

Famous Red Diamonds

Currently, it is estimated that between thirty to fifty red diamonds are known to exist, so each and every one of them are significant gems. However, there are quite a few more that have a secondary hue like the Hancock Red. Let's examine a few stones.

Moussaieff Red Diamond

Weighing an impressive 5.11 cts., the Brazilian shield-cut Moussaieff Red is the largest Fancy Red gem in existence. The diamond came from a rough crystal that was 13.90 ct. That may not seem like an impressive size, especially considering how many 100+ ct. colorless diamonds have been uncovered in recent years, but this stone dwarfs the vast majority of primarily red diamonds that have been found.

The Argyle Everglow

Like many of the important red diamonds from Argyle, the name of this stone includes the title of the mine. Now faceted into a 2.11 ct. radiant-cut, this diamond sold for an undisclosed price in 2017. While we don't know exactly what was paid, it was announced that, at that time, it was the most valuable gem to come from Argyle in its entire history.

The Lady in Red

Like the Hancock Red, the Lady in Red is a purplish Red gem that weighs just over half a carat at 0.54 ct. It is rumored that the current owner of this round brilliant-cut gem was recently entertaining offers "over seven figures."

The Argyle Phoenix

With a selling price over two million, this 1.56 ct. Fancy red round brilliant gem sold at the 2013 tender for the highest price-per-carat value in the history of the Argyle sales.

The Kazanjian Red Diamond

Unlike most of the other red diamonds on this list, the Kazanjian is a diamond with a history. Originally known simply as the "Red Diamond," this 5.05 ct. Asscher cut gem from Lichtenberg, South Africa was unearthed in 1927. Heralded as the second largest red diamond in the world, the stone was confiscated by the Nazis and brought to Germany in 1944. The Americans later found the gem hidden away in a salt mine. It was bought by an anonymous buyer in 1970 and was unaccounted for until 2007 when it was purchased by Douglas Kazanjian, the CEO of Kazanjian, and renamed for him.

How to Care for Your Red Diamond Jewelry

There is no reason to treat red diamonds, natural or synthetic, any differently than you would a colorless diamond. The red hue is caused by graining which does not affect the durability so you can feel free to clean your red diamond jewelry in an ultrasonic machine, use steamers, or any specialized jewelry cleaning solution. See our gemstone jewelry cleaning guide for more recommendations.