How Are Black Diamonds Manufactured and Processed?

Black diamonds are unique in the sense that not many people are aware of it or use it. Most think that diamonds are white or pink if one thinks of various options in terms of colour. But black diamonds are unique and the natural ones are rare. Black diamonds can make excellent jewellery pieces if they are used right. Black diamond rings symbolize love and power at the same time while looking stylish. Before going into how black diamonds are manufactured and processed, we need to know about the type of black diamonds. There are three types – natural, treated and synthetic. Each type has a different manufacturing process.

Natural black diamond:

Natural black diamonds are impure polycrystalline diamonds which is made up of diamond, graphite as well as amorphous carbon. It is a tough form of diamond, dark grey in colour and usually more porous than any other. They are basically an aggregation of small black crystals. Diamonds that occur naturally have colours due to the impurities attached to them during their formation. There could be mineral inclusions such as hematite, pyrite or graphite that make a diamond look black. Most natural black diamonds are opaque giving it a unique look.

Treated black diamond:

Black diamonds can be created by treating naturally occurring white diamonds. If a natural white diamond has a lot of inclusions and hence of low value, jewellers may treat them with heat or irradiation. They become black coloured diamonds and are less expensive in the market.

Synthetic black diamond:

To grow a diamond in the lab, a lot of research and effort goes into it. That is why, it is not common to see a lab-grown black diamond, because there isn’t much demand for it. Because of the low commercial viability of black diamonds, companies instead choose to invest in pink or blue diamonds.

As the most common types of black diamonds are the natural ones or the treated ones, this article will focus on their manufacturing and processing.

Manufacture and processing:

  • As mentioned above, black diamonds can be created in two main ways – naturally or by adding heat. Natural ones are produced just like white diamonds, under a high-pressure environment. It is just that they have a graphite inclusion, giving them a dark colour. Low-value white diamonds can be exposed to high heat or radiation to give them a black colour. The processes used to do this are known as CVD or chemical vapour deposition and HPHT or high-pressure high temperature.
  • Natural black diamonds are hard to cut and polish due to their polycrystalline nature. As such, they take longer to facet and have to be maintained carefully to avoid damage. Treated black diamonds are actually colourless diamonds of low value and they are easier to cut and shape.

Black diamond eternity rings made of natural stones show how important the recipient is as the stones are quite rare and found only in one particular region.


All diamonds are graded based on 4C’s and black diamonds are also subjected to this process. The 4C’s are as follows:

  • Colour

Naturally occurring black diamonds have only one intensity of colour which is fancy black. As the stones are opaque, they don’t vary in the colour’s hue or tone much. So, the system designed to grade stones based on colour doesn’t apply here. It also means that the stones don’t sparkle in the light, adding understated elegance. Black diamond rings are made from natural stones, therefore, are quite expensive.

  • Clarity

Because of the inclusions, black diamonds don’t refract light like other diamonds. Hence, this grading system also doesn’t apply here. Treated diamonds, however, aren’t opaque and can reflect light.

  • Cut

Natural black diamonds are difficult to cut due to the closely packed inclusions. They can have cavities near the surface too, making the job harder. That is why a smooth, well-cut black diamond is far more valuable. Treated black diamonds are easier to handle and cut.

  • Carat

A carat is the weight of the diamond and natural black diamonds may have a higher carat but look smaller. This is again because of its density.

The Value

A black diamond engagement ring can be expensive if it has a natural stone with a good cut and polish. Because there may be difficulties in cutting them, they don’t come in similar sizes. The stones may have a rose cut, small table or a large table cut. A properly polished natural black diamond will add a shiny quality, very different from white diamonds.

Not all jewellers would keep black diamonds or know how to handle them. Hence one must purchase them from an experienced jeweller who understands the processing of diamonds well.

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