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The manner in which the actual work of cutting and polishing gems is performed by the most advanced methods of the present day varies somewhat with the kind of stone. Some stones naturally require a much harder abrasive than others, while different wheels and differ­ent polishing powders are suited to different gems. In general, the stone is reduced as nearly as possible to the desired shape by careful cleaving in the rough. If there is a natural cleavage much use can be made of this in bringing the stone to the desired shape; if not, the work cannot be carried far in this manner. Large stones, if not too hard, can be sawed to a desirable shape with diamond or carbor­undum saws. After having been shaped as nearly as possible by one of these methods, the rough stone is then soldered to a metal handle, or cemented to a stick by means of wax or other adhesive substance, and ground to a rounded symmetrical shape on a flat, revolving wheel, the abrasive used being applied by means of water or oil. The wheels used are generally either of iron or copper, though lead, tin, and even wooden wheels are employed. For all gems except the diamond, the cutting of which can be carried on only by means of diamond dust, emery or ground corundum is the abrasive generally used7 although since the invention of carborundum this is employed quite extensively. After the stone has received a general rounding in this manner, the cutting of facets, one at a time, is begun. To maintain the exact angle at which each facet is to be cut, a clamp is provided above the wheel, in which is fastened the handle on which the gem is soldered. By this means the stone is held against the wheel at the desired angle until the facet is cut. For facetting cheap stones the handle of the gem is sometimes held in the hand; but while the work can be done faster by this means it obviously cannot be performed so accurately. After the stone has received by grinding the proper number of facets, each of the size desired, the work of polishing must be performed. This is done in a similar way to the grinding, except that softer abrasives and softer wheels are used. Rouge, tripoli, and " putty powder " are the abrasives most commonly used for this pur­pose, they being applied dry or moist to wheels of leather, felt, or paper, against which the stone to be polished is held.
Owing to its superlative hardness the cutting of the diamond must be performed by a somewhat different process than that of other stones. The facets upon a diamond are cut by rubbing together by hand two diamonds cemented upon sticks. After the facets have been outlined in this way they are ground and polished upon wheels to which diamond dust is applied, in a manner similar to that described for other gems.
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