Gemcutter

A gemcutter is a person who cuts, shapes, and polishes natural and synthetic gemstones. In historical use it usually refers to an artist who made hardstone carvings or engraved gems, a branch of miniature sculpture or ornament in gemstone.

Among a modern gemcutter's work are the following activities:

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.

The faceting equipment allows for very precise adjustment of angle and location of facet placement around the gemstone referred to as indexing. The facet design may be computer generated or left to the skill and experience of the individual cutting the gemstone.

With the exception of diamonds a coolant is constantly applied to keep the gemstone cool since it is usually held in place on the end of a dop using high temperature shellac based wax, paint or other adhesive. (The dop in this case is a machined brass or stainless steel rod)

...
Wikipedia