Rough Diamonds

Diamonds: A Billion Year Journey

Many people own, wear and love diamonds, but few know the incredible story that brought them from the depths of the earth into their jewellery. They are not only the hardest natural substance on earth, but also one of the oldest. Forming deep in the earth’s mantle over 1 billion years ago, with some of the oldest diamonds dating back over 3.3 billion years, they have a story to tell.

Diamond Formation

Diamonds form in the earth’s mantle, the molten part of the planet deep beneath the crust, about 140 to 190 kilometres beneath the surface. Here, carbon atoms are subjected to extremely high pressure and temperature. The pressures can range from 45,000 to 60,000 times the regular atmospheric pressure at sea-level, with temperatures as high as 1300C. In these extreme conditions, the carbon atoms are forced into a crystalline arrangement, forming diamond. No one is sure where exactly the carbon comes from, but a possible theory is that the carbon may have originated on the surface of the earth in the form of prehistoric plant and animal material, and was subducted into the mantle through plate tectonics. If this theory is correct, the carbon in your diamond may have come from some of the earliest life on earth!

Diamond is the only gemstone made entirely out of one element (not considering inclusions and small amounts of trace impurities). Nature is not always perfect, so often many other minerals or defects will form in the diamond as it grows. These are the inclusions that affect clarity grading. Under heavy magnification, some inclusions can even be identified as other minerals, such as garnet, peridot, zircon and even other diamonds! Other elements may also make their way into the diamonds, causing changes in colour. Nitrogen, for example, causes the yellow colour, while boron causes diamonds to be blue. Eventually the diamonds cool in their host rock, and may wait millions or even billions of years for the right conditions to make their way to the surface.

An Explosive Ride to the Surface

When the right conditions arise, diamonds are brought to the surface during massive volcanic eruptions. These kinds of cataclysmic eruptions are extremely rare. The diamonds hurtle to the surface, carried by streams of magma, rock and gas. During this explosive transport of the stones, they can often be broken or cracked. Many inclusions also form during this stage as the diamonds are battered through crevices in the crust. The diamonds eventually get trapped in these crevices, or they explode onto the surface of the earth along with other rocks and magma. The majority of the best diamonds are trapped within a central core, forming a vertical, triangular area of new rock called a pipe. These pipes often reach the surface, but can extend hundreds or thousands of metres into the earth. The most common type of rock that forms these pipes is called kimberlite, named after the famous town of Kimberley, South Africa, where the first major commercial diamond mine opened.

Finding Diamond Deposits

Nearly all diamonds found today were deposited hundreds of thousands or even millions of years ago. These diamonds are either found in the eroded remains of ancient, extinct volcanoes, still in their pipes, or in riverbeds and oceans where the diamonds had already been eroded out of the volcanic rock and deposited elsewhere by the forces of erosion. Diamonds that are deposited in riverbeds, called an alluvial deposit, can either be found in still-flowing rivers, or they can be found in ancient riverbeds that have now dried up.

Depending of the type of deposit, diamonds can be prospected in multiple different ways. In the case of diamonds still in their host rock, geologists will often find known volcanic pipes, and drill core samples. These samples are analyzed to search for microscopic diamonds, as it is extremely rare for larger diamonds to be deposited close to the surface. The core samples are also analyzed to detect other minerals that could indicate the presence of diamonds. A strong presence of garnet and peridot indicates a possible diamond deposit, as these minerals often form in the same environments as diamond. In the case of alluvial deposits where the diamonds are deposited in rivers, these stones were often found by accident by lucky farmers or swimmers, which led to the opening of mines. In more modern times, geologists analyze records of eroded diamond bearing pipes, and determine how it was eroded and where the diamonds could have been transported to.

Diamond Mining

Depending on the type of deposit, the mining process can look vastly different from mine to mine and from region to region. For diamonds still in their primary pipe deposit, this can look like an open pit mine or a subterranean mine. These two types of mining operations are the most common, and are what most people picture when they think of a mine. In either case, the mine blasts and drills directly into the rock. These rocks are then removed, crushed and bathed in acid. Since diamonds are relatively immune to acid, the rock dissolves away and leaves the diamonds behind. These diamonds are then sent to a sorting facility.

In the case of oceanic or alluvial deposits, the diamonds must be sifted and filtered out of the mud and silt. Since diamonds are quite heavy, they will sink. In smaller alluvial mines, diamonds are found very much in the same way that one pans for gold. Once filtered out, the diamonds are sent for sorting and cutting.

In most diamond producing countries, there are strict regulations on mining processes. Mines are monitored on a regular basis by regulatory committees and government agencies to ensure they abide to environmental, safety and human rights standards. Thanks to the Kimberley Process, a certification scheme that mandates a documented chain of custody for loose diamonds, consumers can be assured that their certified diamond is 100% conflict free. In many cases, mines are also required to abide to a reclamation program, wherein the mined area must be naturalized after the mine closes to ensure no long lasting negative effects on the environmental health of the area. Due to these regulations, diamonds are now one of the most ethical of all mined materials, even when compared to other gemstones like emeralds, rubies and sapphires.

Sorting and Cutting

Sorting takes place in a separate facility. Here, under high security, trained staff sort through the rough diamonds. They sort them into categories based on colour, size, shape and relative clarity. These rough diamonds are then packaged up into large collections of various types, and are sold and shipped to a small handful of diamond cutters. These diamond cutters will first examine the rough stone before cutting it. It is the goal of the diamond cutter to maximize the carat weight of the diamond without any significant sacrifices on quality. That being said, a cutter may decide to optimize carat weight at the expense of cut quality, colour or clarity, so long as it maximizes profit on the stone. Depending on the shape and placement of inclusions in the stone, the cutter may decide to cut the stone into multiple smaller diamonds of various shapes or sizes, or into one large stone. Usually the first scenario is the most common.

Thanks to modern technology, a scanning laser computer is now often used in the industry to map the rough diamond. The computer will then automatically determine the best way to cut the stone to maximize profit on the rough material. Even with this advanced technology, a skilled diamond cutter still has the last say on how to cut the stone.

Diamonds are cut and polished, usually by hand, on a device called a lapidary. A similar technique is used to cut and facet all gemstones. First, the rough diamond is cleaved or laser cut to form the basic shape. The diamond is then attached to the end of a rod called a dop. By placing this rod at certain precise angles and rotations, the diamond can be positioned to precise measurements for cutting and polishing. The diamond is ground against a rotating disc, called a lap, which is coated in water and diamond powder. Since only diamond can cut diamond, a diamond powder is used for this process. By rotating and angling the stones to precise measurements, and grinding the stone using finer and finer grits, the stone is eventually cut and polished.

The Final Steps

Once the stone is cut and polished, and it passes a quality control inspection, it is sent to a gemmological lab to be graded. Once graded, it is sold to distributors, who then sell the stone to manufacturers, who then set the diamond into finished jewellery. They then sell this to a retailer, who eventually sells it to you!

It can take billions of years before a diamond is even mined. Then the process from the mine to the finished piece of jewellery can take months or years to complete, and requires a lot of labour and skill. At Kimberfire, we cut out the middlemen and connect you directly with the diamond cutters and distributors. This way we can provide you with a beautiful diamond, and with the exceptional in-person service you would expect from a high end retailer, but at a fraction of the cost when compared to a traditional store.

Image credits: Lucara Diamond Corp., Rio Tinto’s Diavik Foxfire, Rio Tinto’s Argyle Pink Jubilee

Michael Vander Eyken
Michael is a Diamond and Jewelry Consultant at Kimberfire – a brilliant way to buy engagement rings, fine jewelry and loose diamonds in Toronto. He graduated from the Jewelry Essentials program and the Gemmology program at George Brown College. Before joining Kimberfire, he worked in fine jewelry sales at some of the biggest names in the diamond jewelry business, such as Birks and Tiffany & Co. As an FCGmA certified gemmologist, he lives and breathes diamonds and gemstones. This shows in his large collection of gemstones and mineral specimens that he keeps at home. On his days off, Michael keeps active on his mountain bike and in the swimming pool.
Michael Vander Eyken

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