How do you cut diamonds?

Even though diamonds can be artificially made, they are not true diamonds. True diamonds are created exclusively by nature, forged from the molten magma at the heart of the planet. They are made from carbon, which is actually one of the most common materials in the world. It is their rarity and beauty that make demand for them so high. The most valuable diamonds are those that are completely transparent and show no imperfections whatsoever. So, how do they go from being mined from the earth into the delicate and stunning jewellery that we see in the jewellery stores?

There are several techniques used to cut and shape diamonds before they make it to the glass cabinet display in the jewellers. The process is much more labour intensive than cutting and shaping metals. For larger scale metal items Tapping Machines such as the ones you can see at  Cotswold Machinery will be used, for small pieces these may be manually shaped. But diamonds are much more complicated and it takes years of training before you are deemed skilled enough to cut and shape one of these beautiful gems. Here are the four techniques used:

Cleaving

The diamond must first be cut down to a smaller, more manageable size. A special cutter is used to cleave the stone along its tetrahedral line, the weakest point of the diamond. To hold the diamond in place while it’s cleaved, wax or cement is used to keep it still. The cutter can then cleave a sharp cut along the plane. A steel blade is then placed inside the groove and hit hard so the stone breaks in two.

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Bruiting or Cutting

This is the method employed to give diamonds their shape. When this process is done by hand, it is called bruiting. Cutting refers to the process completed by machine. For hand-shaping a diamond, the person cutting must rely on the toughness of the stone. Diamond is the strongest material one earth, so a cutter uses a diamond to cut the diamond.

The instrument used is like a small stick with a bowl of cement at the end to hold the diamond in place. One corner of the stone is left exposed and the cutter rubs the stone with two sticks. This is known as bruiting. When using a machine, a lathe holds the diamond in position while another diamond is rubbed against it.

Sawing

If a stone shows no tetrahedral plane of weakness, cleaving won’t work. A blade made from phosphor bronze must be used which rotates at around 15,000 rpm. A laser can also cut diamonds, but this process takes many hours. Using a blade, the cutter must choose which area of the stone will become the table (the flat part of a diamond with the largest area) and which part will be suited to become the girdle (the rim with the stone with the biggest point of diameter).

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Polishing

After the cutting process is complete, the diamond’s finished look is created by polishing. The gem is positioned onto an arm of a polishing wheel that will rotate it. The wheel is covered with a diamond powder that’s abrasive and softens and smooths the stone as it is pressed against the wheel and rotated.