How to Cut and Polish Diamonds

Diamond cutting and polishing originated in India, later the art was introduced in Italy and in Paris. Amsterdam has become famous for its diamond cutting. For a long time Amsterdam had the largest cutting and polishing establishments in the world. In the early days of diamond cutting, diamonds were usually cut into square shapes with the corners rounded off. Diamonds are now cut, particularly round. The table top of the stone is surrounded by thirty-two small facets reaching from the table to the girdle, or edge of the stone.

A properly cut diamond should have fifty-eight facets if regularly cut, and fifty nine if cut as a patented polished girdle. One third of the stone should be above the girdle, while two thirds should lie below. The tables should be two fifths the diameter of the stone. The diamond will display the best brilliancy if these proportions are used. A stone that is cut too deep lacks brilliancy, while a stone that is cut too shallow becomes flat, and exhibits the fish-eye effect.

Before the rough diamonds are cut, they are first examined by an expert, who decides how each stone should be treated. The expert marks on the stone with ink which parts of the stone should be removed by cleaving or sawing, in order to get the proper shape. During the first part of cutting rough diamonds, they are generally sawed or cleaved to render them suitable in size for cutting. If a rough diamond has to be cleaved, it is fastened with cement to the end of a wooden holder and a grooved is scratched into the part of the diamond that has to be cleaved. The stone is then held by a clamp and a heavy steel blade is used to tap the back of the diamond, and the stone divides on the line predetermined. This may seem like a simple task, but it takes lots of experience and knowledge of stones.

Diamond sawing has been used for over one hundred years now, and it enables the cutter to divide the stone on any plane, independent of its structure. On the other hand you can only cleave a diamond along its natural cleavage lines. A diamond blade consists of a special alloy that is treated with diamond dust. The cutting of a diamond is a long process, taking several hours to cut one.

After the stone is cleaved or sawed, it is again looked over by an expert. The diamond expert gives the plans for further work on the stone. One of the most important things that the expert must decide is the location of the table. Once decided, the table is then marked with an ink circle.

One the last steps in the diamond refining process is, diamond polishing. Diamonds are polished on a polishing wheel covered with diamond dust and oil. The diamond wheel is made from a special casting of a secret alloy. The diamond wheel revolves twenty-two hundred times a minute. A one carat diamond must spend two to four days on the diamond wheel.

By a perfect diamond is meant is meant in the trade a diamond without flaw or spot that can be discovered through a watchmaker’s eye. Scientifically a perfect diamond does not exist. All diamonds will show some imperfections if a strong enough glass is used. Commercially perfect diamonds and slightly imperfect ones are equally salable.