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Influence of weather on stones

Posted September 24th, 2008 by admin

The influence of time and weather have almost certainly dulled or marked their surfaces, and it is the work of the lapidary to produce a beautiful stone from the piece of unattractive rough material which he is handed. Badly flawed pieces are not usually cut; cleavage, optical properties, and hardness must be considered, and the cutting of stones into definite shapes with definite proportions calls for considerable skill and experience.

Abrasives,” very hard, substances used in the working of gem materials in order to grind away .or polish rough surfaces, are a most important factor in lapidary work. In recent years, several artificial abrasives have been produced, many of which are far superior to natural substances which have long been used. Diamond, however, still remains the hardest substance known, and carbonado and boart, two types of this stone which are used almost exclusively as high grade abrasives, are of great importance in many industries outside of gem cutting.

Corundum, emery, and garnet are also used, as well as the artificial carborundum. Other abrasives are artificial corundum and boron carbide. Corundum is now made by fusing bauxite in the electric furnace, and it is marketed in various forms under different trade names. Boron carbide, or Norbide, is made from a mixture of borax and coke, and it is considerably harder than either corundum or carborundum.