Diamonds and precious stones, a popular account of gems .. . Englishred (anhydrous peroxide of iron). Different wheelsand polishing substances are used according to thekind of stone. The greater part of colourlessprecious stones are cut with the leaden wheel, andwith rotten-stone well moistened. This serves togive the first polish to all precious stones in whichsilica is the principal element—agates, jaspers, hya-cinths, &c. The two styles most employed are the step-cutand the smooth-cut or cabochon. When the latteris very flat it is called the tallow-drop. Each ofthese may be round or oval, e
Diamonds and precious stones, a popular account of gems .. . Englishred (anhydrous peroxide of iron). Different wheelsand polishing substances are used according to thekind of stone. The greater part of colourlessprecious stones are cut with the leaden wheel, andwith rotten-stone well moistened. This serves togive the first polish to all precious stones in whichsilica is the principal element—agates, jaspers, hya-cinths, &c. The two styles most employed are the step-cutand the smooth-cut or cabochon. When the latteris very flat it is called the tallow-drop. Each ofthese may be round or oval, elongated or square. The cabochon is plane, convex or concave on its 28o PRECIOUS STONES. inferior side. In the latter case it is the doublecabochon. Concave cabochons are employed for stones mo-derately transparent, and this disposition tends tofacilitate a more easy transmission of light. Gar-nets of a certain size are often cut in this form; andthis cutting is used especially for the adularia, thecats-eye, the hydrophane, and, above all, the Fig. 121.—Cutting of Precious Stones other than the Diamond. It serves better than any other form to display thespecial beauties of these different stones. The stones cut in step or pavilion form aregenerally not very thick, and there are usually moresteps or degrees on the lower than the upper side;as on the upper part a large table in the centre isgenerally reserved. Figs. 121 and 122 representforms given to a great number of coloured stones,especially the emerald and the oriental aquamarine. There are other forms, in which the stones cutin circles or ovals have a large table on the uppersurface, surrounded with facets, which are either MOUNTING OF PRECIOUS STONES. 281 triangular or triangular and quadrangular both. Inthis case the lower face is covered with quadrilateralfacets, and has a very small table in the centre.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectgems, booksubjectprec
