The cutting and polishing of diamonds are very delicate operations that can be carried out only by skilled craftsmen who pass on their art from one generation to the next.

Not all diamonds can be cut and transformed into elegant stones. The more impure ones and fragments obtained from cutting gems are used in industry. Diamonds are extremely hard and are valuable in cutting or polishing the hardest of metallic alloys.

Another precious stone that is extremely rare and very valuable is the emerald which is a beautiful green color. Emeralds are usually small. When one is larger than ten carats and free from impurities and faults it is much more valuable than a diamond of the same size.

Much of the value of these gems depends on the way they have been cut. The usual way is to cut surfaces or facets on them so that they will refract or break up the light that passes through the stone. The effect is to produce a number of small prisms which break up the light into the beautiful flashing colors of the rainbow. Great skill is necessary at every stage of diamond cutting, but especially during faceting, as the angles of the facets must be exact to give the maximum amount of brilliance and to preserve the symmetry of the stone. The upper part of the faceted gem is called the crown and the lower is called the base or pavilion.