Gem Cutting

About this book

The term gemcutting is used to describe the process of shaping and polishing faceted gemstones. The artisan undertaking the cutting can also be called a lapidary. While the gemstone in the rough state may be trimmed to remove undesirable material or to separate it on a cleavage line with a diamond bladed saw accurately described as cutting and once done by the use of a chisel or similar tool to simply break off pieces that were usable as single gemstones. The actual shaping and polishing of a gemstone is a grinding or sanding process. This grinding and sanding is done using a lap a precision metal plate embedded with grit similar to the more familiar embedding of grit on paper the lap is of high precision particularly for flatness and turned by a motor. (See faceting equipment) The grit material is normally diamond and sometimes corundum for their hardness. Only diamond is hard enough on the Mohs scale to shape and polish a diamond. The initial shaping and facet placement may be done using laps with the more familiar grits of 220 600 1200. The polishing step however requires grits that are less familiar 8 000 14 000 50 000 and even 100 000. This grit is also embedded into a metal lap but sometimes applied manually to the lap during polishing.