When most of us think of diamonds, we picture a sparkling clear gemstone. Many people are unaware that diamonds can come in different colours such as yellow, grey, blue, red, green and even black. Diamonds that have a different colour than clear transparent or faint yellow tinge are called 'fancy colour' diamonds. Of all the possible colours, black is probably the most striking and over the past few years have become popular among those wanting to buy or own an unusual piece of jewellery.

To make life a little harder for buyers of unique diamond jewellery, not all is as it might seem when it comes to black diamonds. While there are natural diamonds, they are quite rare, and thus costly. To supply demand at lower prices, black diamonds are now being made by artificially changing the colour or synthesised in laboratories for use in diamond jewellery. In this article, we will briefly look at the three types of black diamond. You will be an informed buyer when you choose to buy jewellery made with any kind of black diamond. A little knowledge is very useful because there is a significant difference in price between the three types of black diamond.

Natural Black Diamond

Most natural diamonds have inclusions, these are usually small cracks in the diamond, but occasionally they can be cavities. Some diamonds have tiny black spots that can be seen on the flat surface (the table) of a stone. In a natural black diamond, the incursions are filled with graphite or sulphides and are numerous enough to render the diamond in a dark, black colour.

There is a second form of naturally occurring black diamond called Carbonado. A Carbonado is a rare form of diamond that differs in several ways from typical diamonds. The diamonds that are usually found in jewellery are a single crystal of carbon that has undergone colossal pressure and temperatures and for billions of years. This process changes the carbon black to the single, clear crystals that are cut to make jewellery. A Carbonado is not a single crystal, but a different form of diamond made up of a multitude of tiny crystals with impurities of graphite and non-crystalline (amorphous) carbon between the microscopic diamond crystals. This combination gives rise to a rare form of diamond that is even tougher than a regular diamond with the characteristic black colour.

Some experts think that Carbonado diamonds did not originate on Earth but fell to Earth following a supernova almost 4 billion years ago. Evidence for this is seen in the geographical location of all Carbonados. There are only two places in the world where these gems are found, Brazil and the Central African Republic. Although these places are on opposite sides of the Atlantic Ocean, in the distant past these areas were part of the same region of land that split to form Africa and South America.

Buying Hint: Before purchasing a black diamond, always ask the seller what type of diamond it is. If you want a natural black diamond, you do not want to be fobbed off with the cheaper artificial or treated stones.

Enhanced Black Diamonds

Because they are so rare and expensive, most black diamonds sold in jewellery stores are treated to make them appear black. The process works by taking a diamond that is already coloured, often a grey or green gem, and exposing it to radiation. The radiation moves atoms around in the diamond, causing a permanent colour change, in this case to black. After exposure to radiation, the newly black diamond is treated using heat in a process called annealing that renders the colour change permanent.

Although the diamond has been exposed to radiation, it is entirely safe. Irradiation of diamonds to change their colour was first carried out in 1905 by the English chemist sir Williams Crooke. The earliest colour changed diamonds were not safe for use in jewellery because they carried radioactivity from the irradiation process. The irradiation process used today is entirely safe.

Irradiation is usually carried out on relatively low-quality stones where the colour change masks imperfections in the gem. This is good for buyers because the cost of an irradiated stone is much cheaper than a natural stone of equivalent carat weight.When buying a black diamond lookout for the term 'earth mined'; these words are designed to reassure buyers that the diamond is real. Unfortunately, usually, this is a sign that the stone has been artificially treated to create the colour.

Synthetic Black Diamonds

The last type of black diamond is artificial black diamonds, these are very inexpensive and usually very small. This type of stone will not usually be found in a reputable jeweller's stock but can be found on sites such as Ali Baba and Amazon for just a few pounds. Synthetic black diamonds are made in specialist labs using various methods. The best synthetic diamonds can be hard to distinguish from natural diamond but should be avoided if you are seeking a high-quality piece that will become an investment or heirloom. The black colour of such stones is obtained in the same way as for enhanced black diamonds.

Get the Black Diamond You Paid For

The leading certification laboratory for diamonds, the GIA, offers certification for black diamonds using slightly different criteria and in the form of a Colored Diamond Identification and Origin Report. Importantly, the report specifies whether the diamond is naturally black or has been treated to make it appear black. Cheap stones will not be graded by reputable gemological labs due to the cost of doing so.

Caring For Your Black Diamond

Because both natural and treated black diamonds have many inclusions, it is essential to clean the stones carefully. The GIA recommends that such stone should not be cleaned using ultrasonic or steam cleaning techniques. Cleaning should be done in the same way as for other delicate gemstones.

The people who choose black diamonds for their jewellery will tend to be people who like to create an impact. A black diamond engagement ring can make a stunning statement. The inky blackness will always attract attention. Even though black diamonds are increasing in popularity, they are much rarer than common clear diamonds.