LAPIDARY WORK. The work of the lapidary is that of reducing, shaping, grinding, and polishing small hard pieces of stone, especially those which go by the names of gems or precious stones. Such stones require different modes of treatment according to their hardness. The diamond, sapphire, ruby, chrysoberyl, and zircon rank among the very hardest ; the agate, amethyst, agnainarina, bloodstone, carnelian, car buncle, cat's-eye, chalcedony, chrysolite, chrysoprase, crystal, emerald, felspar, flint, fluor-spar, garnet, granite, jade, jasper, lapis-lazuli, onyx, opal, porphyry, quartz, sardonyx, serpentine, and topaz, though differing much among themselves in hardness, may be considered as occupying a sort of medium rank ; while a softer class of minerals and vitreous substances is that which ineludes alabaster, cannel coal, coral, enamel, glass, jet, lava, malachite, mother of pearl, satinstone, steatite, &c. It is by means of small revolving wheels that these are cut and polished by the lapidary. The wheels are of iron, lead, wood, and other substances. For cutting, the edge of the wheel is sharp, and is touched with moistened diamond powder, emery powder, or some similar material ; and the edge then acts like an exquisitely fine saw, which works its way through the hardest gems when applied to it. For polishing, the gem or stone is held more frequently against the side of the revolving wheel, or else against buff-leather fixed to the edge of a broader wheel. One of the most delicate examples of lapidary-work ever executed was the shaping of the world-renowned Koh-i-noor, or "mountain of light," the large diamond obtained by Queen Victoria from the chief of the Punjab. This jewel, large and fine as it is,
was found to have been badlsr and facetted ; Professor Tennant - and the Iter. 11r. Mitchell. on having the 'subject submitted to them, reported that the brilliancy of the diamond might be increased by a careful resitting. Masers. Garrard were entrusted with the work ; theyI the services of M. Coster of Amsterdam, the moat highly. In Europe; Messrs. Maudelay and Field made a small steam-engine. and constructed a revolving apparatus, expressly for the purpose; and the late Duke of Wellington cut the first facet, as an amateur who took great interest in the matter, n few months before his deals in 1852. The process of wholly reshaping the diamond occupied several weeks, on account of the extreme precautions necessary in dealing with a gem of such enormous value. Elaborate as the arrangement, were, the lapidary-work was essentially the same In this as in other Instances—the friction of a rapidly revolving metal wheel moistened with diamond-powder and water.
The practical applications of the art will be found illustrated in such articles as CAMNO ; Glass Maeoraorret, Glaueagraring ; INTAGLIO; and also in some of the mineralogical articles in the NAT. IIIST. DIV.