What is black diamond?

Answer 1

Black diamonds are kind of a paradox. They're real, but they don't do the thing that makes diamonds interesting. They don't sparkle, because they're black. They absorb light rather than refract it.

They are real diamonds, but they have a different crystalline structure. The regular crystal structure of the diamond is what causes the sparkle: light comes in, bounces around in a predictable way, and is bounced out. The cut of the diamond is designed to put "windows" precisely where the light will come out to best effect.

Black diamond's have a "polycrystalline" structure, which means it's kind of like many diamonds smashed together. Since they're all at different angles, and so you can't carve it to make sparkles. Instead, the light just gets absorbed, making it black.

It's still a pure carbon crystal, so they call it at "Carbonado", but it is technically a diamond. Just not a very attractive one. Diamond stores generally sell them at about the same price as white diamonds as exotic diamonds, but they don't sell nearly as well because they're not very pretty. They used to be cheaper than white diamonds, but a concerted marketing campaign has driven up the price.

Another Answer

A black diamond is a diamond mineral called carbonado.

According to Wikipedia: "...['black diamond'] is a natural polycrystalline diamond found in alluvial deposits in the Central African Republic and in Brazil. Its natural colour is black or dark grey, and it is more porous than other diamonds."