Polished Baroques And Cabochons
TUMBLE-POLISHED BAROQUES AND CABOCHONS
Large quantities of irregularly-shaped gems, known as baroques or tumbled gems, are now prepared very cheaply by tumbling pieces of rough in barrels along with suitable abrasives and liquids, and later, with polishing agents. The process takes many days or even weeks, depending on the kind of material, the size of the barrels, and other variables which are carefully considered by the manufacturers.
While the principal tumbled-stone production remains baroques, an increasingly important segment has become the smoothing and polishing of geometrical shapes, including cabochons. Many of the cuff-link gems sold today in clothing shops are tumbled. They begin as small sawed squares or other suitable shapes and are merely placed in the tumbling barrels until they eventually emerge as polished gems. In the case of cabochons, the shaping must still be done by hand methods, but the te¬dious final smoothing operations can be accomplished by tumbling. The drawback to this method of finishing is the tendency for all sharp edges to become severely rounded. In some kinds of jewelry mountings this is not of importance, but in others it is, and the traditional, completely hand-finished cabochons are still employed in many kinds of jewelry. Balancing the drawback of rounded edges is the fact that the tumbling operation often produces a vastly superior finish on certain gemstones which are hand-polished only with much difficulty and the expenditure of much time, for example, jadeite, certain jaspers, and rhodonite.
While it is true that flawed and cracked material can be fruitfully employed as grist for the tumbling mill, there is a fallacy among some makers of tumbled gems that any rough, regardless of how poor it is, is suitable for tumbling. Unfortunately, in this field, as in other lapidary fields, there is no art of the lapidary that can improve the intrinsic quality of rough material. If it is poor to begin with, tumbling will only make this fact clearer.
Much of the charm of tumbled gems lies in their irregular shapes, but if the shapes are too irregular, it becomes nearly impossible to smooth those places which are deeply recessed or which follow large, open cracks. As with other lapidary objects, the best tumbled gems are made from colorful or attractively patterned material, free from unsightly cracks, flaws, and soft spots, and are polished to perfection. To be avoided are those pieces which have been tumbled so violently that they retain nu¬merous surface cracks or rough spots upon protruding places. Other signs of poor workmanship are cracks filled with polishing compound, chipped places, and unpolished spots in deep recesses.
Tumbled gems must be fitted with attachment eyes. There are several suspension methods used: (a) a groove is cut around the gem and a thin wire is fitted into the grove and twisted into a suspension loop at one end; (b) an ornamental cap is cemented onto the stone with epoxy; and (c) a small, narrow groove is cut in one end of the stone and a metal ring is cemented into the groove with epoxy. The last of these methods is far superior in holding power to the others and should be specified where high-class stones are involved.