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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:
- Positioning rough stone in a holder, and holding the stone against the edge of a revolving saw or lapidary slitter impregnated with diamond dust to cut and slit stone.
- Removing cut stone and placing it in lapidary stick. A gemcutter then selects the shaping wheel and applies abrasive compound. They hold a lapidary stick against the revolving shaping wheel and lapidary disk to further shape stone and grind facets.
- Examining stone for accuracy of cut, using a magnifying glass. A gemcutter polishes stone, using felt or canvas-covered polishing wheel, and polishing compounds, such as tripoli or jeweler's rouge.
- Possibly using a mechanical facet-cutting device. A gemcutter may cut and polish diamonds for industrial purposes, and be designated as an Industrial-Diamond Polisher (jewelry-silver.).
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.
During grinding, faceting, and lapping, the gemstone is usually fixed ("dopped") to the end of a wood, brass, or steel rod (a "dop" or "dopstick") with dopping cement, a specialized thermal adhesive. The dopstick can be held by hand, or inserted into the indexing equipment for precise faceting. A coolant then needs to be constantly applied to prevent softening of the cement.
Diamonds however are held mechanically, or with a low-melting tin-lead solder, since the heat generated by friction can be extreme and will not allow the use of adhesives.
Cabochons, smooth shaped gemstones without facets such as jade or turquoise and most gemstones, are shaped and polished in much the same manner, but are usually done by hand relying on the skill of the individual and the use of equipment similar to that shown as lapping equipment