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Attaching the diamond

Posted April 10th, 2009 by admin

As for the stone being worked, this is attached to a holder by means of cement and is only once re-set. The holder is held in the hand, and the required position is maintained by the other pointed end being placed in a vertical spindle which has been pierced at suitable intervals. Mechanical power is used, except in very delicate work. Polishing is carried out on pewter or wooden laps which are sometimes leather or cloth faced. Various degrees of hardness in polishing materials, such as rotten stone, may be had, and special mechanical holders are employed in cutting. Rotten stone is often used for polishing ruby, sapphire, and emerald by London lapidaries.

On the Continent, tripoli powder is more generally used for polishing stones. Spinel is best polished by a mixture of magnesia and rotten stone. Another widely used material is putty powder, which is a dioxide of tin from the crude oxide, formed on the surface of melted tin. Pumice stone is another material much in use. Almost each stone varies, and experience is the chief guide to the lapidary. For instance, spinel is softer than corundum, but it is not so easy to work. Ruby is tougher than sapphire, and alexandrite is more difficult to work than sapphire despite its lower hardness. Zircons vary; the greens are cut with rotten stone or on a wet wheel alone, and polishing is done with a slowly rotating wheel.