While they don’t sparkle the same way white diamonds do, black diamonds provide stunning contrasts in all kinds of jewelry. Black diamonds can dress up or dress down an outfit and provide an alternative to other gemstones such as black onyx. When paired with white diamonds, black diamonds have an elegance uniquely their own. In recent times their popularity has grown, but what most people don’t realize is that these diamonds are not actually black at all.
So if black diamonds aren’t actually black, what are they?
Like almost all coloured diamonds, natural black diamonds are extremely rare. They are technically white diamonds that are heavily included (mostly graphite). They appear opaque because of their “polycrystalline” structure which prevents them from reflecting light. A natural black diamond is usually given the colour grade ‘Fancy Black’ by grading labs such as the Gemological Institute of America (GIA).
Due to the comparatively high price and scarcity of opaque natural black diamonds, almost all the black diamonds you see in jewellery today are treated black diamonds. Treatment, in the form of irradiation or heat, is done to enhance their colour. The process actually turns the natural diamond to become a green that’s so dark it appears black, but not opaque.
The treatment process doesn’t affect the durability of these diamonds, however, because ‘black’ diamonds are heavily included and porous, they’re harder to cut and polish. This can result in blemishes and nicks on the surface of many black diamonds. When buying black diamonds, make sure the surface of the diamond is smooth and well polished. There are definitely varying quality grades, even amongst the treated black diamonds.
How much do black diamonds cost?
The price of black diamonds are lower than white diamonds, mainly because of the colour treatment. Typically, a 1 carat round treated black diamond with a nice make and excellent polish (no surface blemishes) will cost in the neighbourhood of US$400 - US$600 per carat. In contrast, a decent 1 carat “near colorless” diamond with an average clarity, such as VS1 or VS2, will cost approximately US$5000 — US$8000/ct.
Remember, natural black diamonds are prized because they are untreated and rare, so expect to pay a substantial premium for them, versus equivalent sized treated black diamonds.