What are Black Diamonds?
Black diamonds are unique, opaque neutral ‘colored’ alternatives to the traditional white, sparkly diamond you're probably familar with. Technically, black diamonds have a very high number of inclusions. Inclusions on a regular white diamond may show up as a tiny dark spot, but many black diamonds appear black as a result of MANY of these inclusions overlapping. The 'black' of a black diamond is technically formed by chemical impurities.
Black diamonds make bold, interesting engagement ring options that feature high contrast and are sure to start conversations.
How to evaluate a Black Diamond
Color and Clarity
Black diamonds are evaluated differently than a traditional colorless or white diamond would be. There are two different sources of 'black' when it comes to black diamonds: 'Fancy' black natural diamonds and treated black diamonds (not referred to as 'fancy'). Both forms of diamonds are highly included, and thus the normal standards of evaluating clarity do not apply.
Natural black diamonds are the more rare of the two, while treated black diamonds have been modified (either by heat, irradiation, or pressure) in order to make them appear more black. Typically treated diamonds begin as heavily included white or grayish white stones that are 'industrial' grade.
In contrast, natural black diamonds are black at origin and have not been treated to become so. These have many inclusions present, but their inclusions form clusters of graphite, which naturally give the stone a black appearance. The way in which natural black diamonds form actually makes them quite rare. This makes them valuable -- much more so than the more commonly available (and less expensive) treated version. Unfortunately, the practice of treating diamonds is somewhat widespread and difficult to decipher, even for professionals. If it's important to you that you have an untreated diamond -- be sure to work with a reputable jeweler who has reliable sources, and always be wary of anything that is priced too low.
One interesting factor related to a black diamond's clarity is it's durability. Technically they still score a 10 (the highest possible) on the Mohs scale (a standard scale of mineral hardness), however it is actually typically even harder than a traditional white diamond. A white diamond’s structure is composed of solid crystal with identifiable naturally occurring lines, but black diamonds are a little different -- being comprised of many small crystals stuck together in a randomized pattern. Because of their superior durability, black diamonds were used for a variety of industrial purposes long before they became cut for jewelry.
Black diamonds are not cut to achieve brilliance or fire, so they are often cut for symmetry, weight, visual size, and/or shape. As a result, it is common to find proportions that do not adhere to the ‘ideal’ standards of colorless diamonds. Because light does not pass through the opaque stones, it's also common to find rose cut or flat backed stones that appear larger in visual size for their relative carat weight.
Rarity and Cost
One of the best parts about some black diamonds is that that they are significantly less popular than other types of diamonds, making them a possible economical option for those who love their unique look. When one considers the availability of treated black diamonds, one can also assume that they are much more readily available. When purchasing a treated black diamond, one can spend less or opt for a larger stone when compared to a traditional colorless diamond or other colored diamonds.
It is important, however, to make a distinction between treated and untreated stones when considering price. Untreated 'fancy' black diamonds are extremely rare, and can command a very high price as a result. For a point of reference: Around one in every 10,000 natural diamonds are colored, and only a small number of these colors are naturally occuring black diamonds.
FUN FACT: 'Carbonados' are a special form of black diamond that are also naturally occurring, but they are only found in Brazil and Central Africa. Scientists believe that these stones originated from a meteorite, and essentially come from outer space. Carbonados, as a result, are some of the rarest of the rare!