Cultured Diamonds

Cultured diamonds - adding colour to quality jewelry

Dr Garth Cambray

Cultured diamonds. Image © Cultured Diamond Foundation

Globally, diamonds are big business. Creativity and science combine to add new high quality coloured cultured diamonds to the jewelers selection.

In the 15th century a major goal of alchemy was to turn lead to gold. Around this period, the only naturally occurring seam of graphite was found in England - few would have guessed that turning lead to gold would never be profitable or even possible, but, that one day graphite would be turned into diamond on a commercial scale, essentially turning one of the softest substances in the Universe into the hardest one.

Graphite and diamond are both allotropes of carbon. This means that graphite and diamond are both composed of carbon atoms, but the way the atoms are arranged and related to each other in graphite and diamond are different in much the same way that in a building different brick laying styles give walls of different strengths and durability. In nature, graphite exposed to high pressures and temperatures deep below the surface of the Earth converts rapidly into diamond - the presence of impurities in the graphite and surrounding factors such as mechanical stress and radiation determine the colour of the diamond. Hence, small amounts of nitrogen will give yellow or orange diamonds, while the presence of boron gas will give a blue diamond. Generally however, the majority of diamonds formed within the Earth are without much colour, and coloured diamonds, when found, command very high prices.

In order for a diamond to be produced in a laboratory, or in industry, the conditions under which diamonds form in the Earth's crust have to be duplicated. For many years various technologies have existed which produce small diamonds in culturing tanks - often these diamonds were not gemstone quality, and found a use instead as industrial abrasives, where small particles of diamond are included in the blades of saws and other tools which benefit from the hardness and durability of the diamond.

In more recent years, world leading diamond culturing technology was developed by Gemesis, a company formed to commercialize research conducted on diamond synthesis at the Gainesville campus of the University of Florida. The technology used is based on that developed in Russia in the 60's and 70's combining high pressure and heat to convert graphite to diamond. With all technologies, much of the trick to using the technology is based on knowledge which is built up with time, hence the so called tacit knowledge built up by Gemesis has allowed it to produce some of the highest quality diamonds on Earth.

Green and blue diamonds. Image © Cultured Diamond Foundation

Each diamond culturing machine is approximately the size of a washing machine and draws about the same amount of electricity as a hairdryer. The machine is seeded with a microscopic diamond crystal and graphite is introduced. Over a period of 3-4 days the machine holds a constant environment of 28 000 Atmospheres of pressure and 1500°C. Depending on the type of stone desired, different elements are allowed into the chamber to dope the diamonds - nitrogen for yellow to orange diamonds, boron for blue stones. In the case of nitrogen, approximately one in 20 000 carbon atoms in the diamond is substituted with nitrogen giving the blue colour. Rarer coloured diamonds include greens, black and recently technology to produce pink diamonds has been introduced, although these will only be marketed next year.

The end products are quite variable, but normally a rough diamond of 2-3 carats is produced. A carat is a term used by jewelers to describe the weight of a gemstone. Each carat is 0.2 of a gram hence the diamonds produced weigh about 0.4-0.6g, with the finished cut and polished stones produced from these diamonds typically being 1 - 1.75 carats.

A diamond by any other name

There are a number of common mistakes people make when thinking about cultured diamonds. A cultured diamond is a diamond, produced under the same conditions that mined diamonds were produced under the ground - high temperature and pressure. Cultured diamonds are identical to mined diamonds in terms of hardness and composition. Diamond substitutes are other chemicals which look a bit like diamonds, but are less expensive - these include cubic zirconia, which are synthesized from zirconium oxide, and are in no way similar to diamonds, other than certain aspects of their appearance.

Cultured diamonds are expensive to produce, hence, price wise, a cultured diamond will not be very different in price to a mined diamond. One of the unique aspects of diamond culturing is however the ability to produce diamonds with colour - generally mined diamonds with colour are very rare, and hence very expensive. Cultured diamonds allow the jeweler to use a greater variety of diamond colours to produce exquisite pieces of jewelry, and increasingly, cultured and mined diamonds are combined in pieces to allow the appearances of each stone to complement the other.

What do cultured diamonds mean to global diamond production? Currently cultured gemstone diamonds amount to 100 000 carats per annum (20kg) and global mined diamonds averaged 168 million carats (33.6 tons) per year from 2001-2005. Mike Goch, Executive Director of the Cultured Diamond Foundation explained that the cultured diamond industry is not in competition with the mined diamond industry, but is actually working together with major role players in the mined diamond industry to ensure that this new addition to the world of diamonds grows the industry and increases the range of beautiful diamonds available to the consumer.

Although Gemesis is based in the USA, much of the diamonds it produces are brought to South Africa where 30 expert diamond cutters, trained in the art and science of cutting these round diamonds, convert them into world class cut diamonds which continue in the same tradition as the world class mined diamonds that have made South Africa famous.