Despite their reputation for being elusive and exclusive, diamonds are actually among the most common gems on Earth. But not all diamonds are created equally, and exceptionally rare diamonds do exist. The rarity and value of such diamonds depend on the elements present in the diamonds, their color and the environmental factors present during their formation. Grab your loupes and let the rare diamond inspecting begin!
What determines a diamond’s value?
Before rarity, all diamonds are graded using the 4Cs: Cut, Color, Clarity and Carat. These factors can significantly impact a diamond's value. As one would expect, the higher rated a diamond is within each of the 4C categories, the higher its value will typically be. However, there are other factors that can increase or decrease the value of a diamond, especially as it pertains to rare diamonds. For example, diamonds with historical significance, such as those with an intriguing, documented history or a link to famous individuals will draw a higher price. Having a certified grading report for a rare diamond can also bring a higher value as well as a vote of confidence in the gem’s quality. Simple factors such as market demand can impact a diamond’s value. For example, as the popularity of specific diamond cuts can ebb and flow, their values are impacted. Similarly, the presence of fluorescence is another factor that can impact a diamond’s value either positively or negatively. Strong fluorescence can affect a diamond’s brilliance and make them appear cloudy, lowering its value. However, some fancy-colored diamonds, such as yellows, can appear brighter with the presence of fluorescence, impacting its value.
Rarest diamonds by color
Boldly colored diamonds can be rare and hold great value, depending on the color. Colored diamonds are graded in order of increasing color strength, from Faint, Very Light, Light, Fancy Light and Fancy to Fancy Intense, Fancy Vivid, Fancy Dark and Fancy Deep. The more valuable diamonds tend to fall within the Fancy Intense and Fancy Vivid grades.
The color of a diamond depends on its elemental and structural makeup. Diamonds containing elements such as nickel and nitrogen tend to be more yellow or brown in appearance. Since these elements are some of the most commonly found elements on Earth, it makes sense that these colored diamonds are more common. On the other hand, diamonds composed of rarer elements or that are formed in peculiar environments and circumstances are rarer and therefore more valuable.
Rare red
The trophy for “rarest diamond color” goes to the red diamond. They were so rare, in fact, that there was a 30-year gap (1957-1987) in which no pure red colored diamonds were graded by the Gemological Institute of America (GIA).
Red diamonds could be found at the now closed Argyle mine in Western Australia, where Earth’s shifting plate tectonics placed stress on diamonds over millions of years. When a diamond experiences stress due to a collision like this, carbon atoms can shift within the diamond. If they shift just right, these newly relocated carbon atoms can cause light to be absorbed and transmitted differently than they would have pre-collision.
Only three red diamonds with a weight of more than five carats exist. Most jewelry aficionados rightfully heap all the attention and praise on the 5.11 carat Moussaieff Red Diamond. But another renowned red diamond is the Kazanjian Red Diamond. Weighing in at 5.05 carats, the emerald-cut stone is housed at the Smithsonian’s National Museum of Natural History. Its deep red color caused it to be mistaken for a ruby for many years.
Beautiful blues
Diamonds containing the chemical boron can have a faint or deep blue color. The more boron present, the deeper the blue coloring will be. Blue diamonds form in places where one tectonic plate is pushed deeper in the Earth’s mantle by another. This subduction brings boron to lower depths within the earth, providing the perfect ingredients and environment for a rare blue diamond to form.
The Hope Diamond is a whopping 45.52 carat blue diamond that also currently calls the National Museum of Natural History its home. Containing boron, the Hope Diamond is a whopping 112-carat diamond, likely pulled from the Kollur mine in Golconda, India. Its deep coloring includes a very slight violet element that cannot be seen by the naked eye.
Gorgeous green
Truly unique and stunning, green diamonds are also quite rare. Most green diamonds are formed through radiation exposure underground, caused by the decay of nearby elements such as uranium. This radiation results in carbon atoms within the diamond being “knocked out of place,” leaving vacancies or “empty pockets” within the diamond. These vacancies and the existence of other elements such as nitrogen, hydrogen and nickel (very rare!) result in blue and red light being absorbed into the diamond, leaving green light to be emitted and seen by the human eye.
The Dresden Green Diamond is among the rarest gems on the planet, weighing in at 41 carats. It is the biggest natural green diamond ever discovered and is currently housed at The Green Vault Museum in Dresden, Germany. The diamond’s low nitrogen and boron levels result in an almost-flawless diamond, with color evenly distributed, increasing its rarity.
Opulent orange
Like yellow diamonds, orange diamonds are formed due to the presence of nitrogen. However, when the nitrogen is deeper inside a diamond (ever so slightly!), light refracts differently, toward a more yellow-red blend, creating an orange appearance.
“The Orange,” a fancy vivid orange diamond, is a marvel of a rock, tipping the scales at 14.82 carats. It sold for $35.5 million in 2013. Another orange diamond, Pumpkin, is a 5.54 carat fancy vivid orange South African diamond, sold just one day before Halloween in 1997 for $1.3 million. It is estimated that only 0.05% of all-natural fancy color diamonds are of the pure, unmodified orange variety.
Pretty pink
Pink and red diamonds are considered part of the same spectrum but are categorized differently due to the significant color variation. Pink diamonds have a weaker saturation, meaning their color is lighter and softer. They can range from a delicate blush pink to a more vivid rose. Pink diamonds are more commonly available than red diamonds but are still rare.
The Graff Pink Diamond was a gargantuan 24.78 carat, emerald-cut fancy intense pink diamond. The combination of sensational coloring and an uncommon cut (emerald cuts are typically associated with white diamonds) dial up the rarity of this beautiful stone.
Interestingly, the diamond’s owner, Laurence Graff, had the diamond’s 25 natural flaws removed using modern technology; an astonishing accomplishment, considering one wrong move could have shattered the precious gem. The “renovations” to the diamond cost it 0.9 carats in weight, a reasonable tradeoff to achieve near perfection.
Rarest diamonds by type
The makeup of a diamond can differ greatly from one to the next. While all diamonds come from carbon, the amount of other trace elements within a diamond and how these elements are arranged determine the diamond type. Since nitrogen is an incredibly abundant element on Earth, it often gets incorporated into a diamond’s crystal structure during formation, making finding a diamond without nitrogen quite rare. Diamonds categorized as “Type I” have detectable nitrogen present, while “Type II” diamonds do not contain detectable nitrogen. Here are the four diamond types, from rarest to least rare:
Type IIA diamonds
No nitrogen is detectable. Diamonds in this category are the rarest, making up less than 2% of all diamonds. Their brilliance makes Type IIA diamonds great options for high-end jewelry. The Graff Pink Diamond, mentioned above, is graded Type IIA.
Type IB diamonds
Nitrogen is present, but only single nitrogen atoms exist; no nitrogen “clusters”. The location of these atoms within the diamond can cause them to be a variety of colors, including yellow, brown and orange. These vibrant, unique hues make them very valuable and popular choices for fancy colored diamond jewelry.
Type IIB diamonds
No nitrogen is detectable, and boron is present. Don't let the "IIB" label fool you – these diamonds are still considered extremely rare. What sets them apart is the presence of boron atoms, which can give them a beautiful blue hue. The Hope Diamond is graded Type IIB.
Type IA diamonds
Nitrogen is present with clusters of two and four nitrogen atoms. Type IA diamonds are the most frequently encountered type, accounting for roughly 95% of all gem diamonds. The nitrogen can give them a faint yellow color.
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