The origins of rock and gem cutting, known today as lapidary, began in the Stone Age. To aid in hunting, prehistoric humans shaped rock and other rigid material to use as weapons and tools. Modern gem cutting originated in China where lapidaries in the Zhou Dynasty carved jade, serpentine and other gemstones for ceremonial and functional purposes in the third century B.C. Modern rock and gem cutting tools are motorised, but achieve the same purposes as those of our gem-cutting predecessors.
One of the first steps in rock and gem cutting is to create the rough cabochon. The cabochon is the basic shape from which the final gemstone is derived and is cut from a slab or chunk of raw material. Using a marker and design template, an outline is marked on the raw material. A trim saw blade then cuts the cabochon just outside the template outlines. Similar in appearance to a round wood saw, the trim saw has a silicon carbide or diamond blade and a water drip to ease the cutting of stone.
Once the cabochon has been cut to just outside the marked template lines, grinding and shaping may occur. Rather than a rotating saw blade, the grinder/shaper has an abrasive diamond-finished spinning drum that grinds the rough-cut gemstone into shape. Many trim saws come with a conversion kit to change out the trim saw blade with the grinder/shaper drum. Grinding removes the excess material outside the template outlines to more closely shape the cabochon to its final design.
Dop Pot and Stick
The final steps of cabochon shaping require more precise manipulation and control of the gemstone. To accomplish this, lapidaries attach the gemstone to a handle or stick, called a dop stick, using hot wax. The dop stick is a simple wooden dowel, about 1/8-inch thick. The hot wax is warmed in a dop pot. Once cooled, the wax is easily removed after stone shaping is completed.
Flat Lap Machine
Once mounted to the dop stick, final grinding of the cabochon takes place. The flat lap machine accomplishes this with fine precision. The grinding disk spins flat, like a record player, instead of vertically, like the grinder/shaper. The disks have a diamond surface and range from a coarse 170 grit to a very fine 1,200 grit. With the gemstone attached to the dop stick, lapidaries use speed and pressure to smooth the cabochon to its final shape before polishing may occur.
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