How Are Diamonds Cut?

In their most natural form, diamonds are, well, quite ugly. They have no luster or shine, and in fact, look like nothing more than broken glass. A diamond must be cut, and then polished before it actually becomes a thing of beauty.

Planning and Marking

A rough diamond is first examined by a planner to determined how it should be cut to yield the best value. The planner takes into consideration of the grain and crystal structure of the diamond to mark positions where it would be cleaved or sawed by the diamond cutters.

Cleaving

Large diamonds are separated into smaller pieces, by a process known as cleaving, that are suitable for further sawing. Cleaving is also done to quickly remove large unwanted pieces (usually areas with blemishes and other imperfections) from the rough diamond. This process is important as a wrong split will ruin the diamond and reduce the value of the diamond drastically.

The cleaver carefully cut grooves into the diamond at locations marked by the planner with another diamond. He then splits the diamond along the grooves with a mallet and a metal wedge. The diamond is now ready for sawing.

Sawing

Sawing shapes the diamond into various shapes such as heart, square, or the common round shapes. A circular disk saw is used to cut it down to shape. The cutting edge of the saw is initially coated with diamond dust in order to start the first few cuts. After the first few cuts, the cutting edge of the saw will coat itself with diamond dust from the diamond that is being cut. This maintains the hardness of the saw's cutting edge.

Girdling

The diamond is further shaped and its freshly cut edges are rounded by girdling. The diamond is mounted on a lathe and another diamond is used to grind it into shape.

Faceting

A diamond lapper or scaife that is coated with diamond dust is used to cut the facets. Faceting is the final and one of the most important steps in diamond cutting where the facets of a diamond is cut. The quality of the faceting that is being done will determine the brillance and fire of the diamond. Each facet of the diamond must be carefully cut into the geometrical shapes that allow maximum refraction and reflection of incident light.

Polishing

Polishing is the final step to transform a rough diamond into a diamond that is ready for sale. A diamond lapper is used, but with a different, finer lapping disk. The diamond is then finally ready for certification grading and sales or further setting into jewellery.

Diamond Carat Weight

The Carat

Diamonds are measured in the unit weight carat. One carat weighs 200 milligrams, and is subdivided into 100 points with each point equal to 2 milligram. The word carat comes from the word carob. A carob is a bean that grows on a tree in the Mediterranean. In times past, if a diamond weighed the same as a carob bean, it was one carob, or one carat.

The Grain

A diamond is also referred to as four grains, this means that it is a one carat diamond. In the far east where carob trees do not grow, rice was used to measure the weight of a diamond. If a diamond weighed as much as four grains of rice, it was four grains – or one carat as we know it to be now.

Carat Total Weight

The majority of diamond purchases are for diamonds that are 1/3 of a carat. Beware when shopping for diamonds that are already set or mounted. If more than one diamond is used in the piece, the tag on the jewellery will give the CTW or Carat Total Weight – it does not tell you the carat weight of each stone in the piece.

Remember, two 1/2 carat diamonds is not equivalent to a 1 carat diamond, pricewise, due to the rare nature of larger diamonds. You need to ask the jeweller for the carat weight of the largest diamond in the piece to truly understand what you are buying.