LAPIDARY WORK (Lat. lapidaries, relat ing to a stone, from lapis, stone). The art of cutting, grinding, and polishing precious stone,. 'This industry has been practiced, in a crude way, from very ancient times. At first only the natural faces, caused by the crystallographic structure of the gene, were polished, but soon the art of enhancing the beauty of the gem by cut ting additional face., or facets, was learned. al though no attempt was made by the earliest lapidaries to give the gem a symmetrical form. Often the facets were elaborately carved and a hole drilled through the centre, so that the stones might be strung like beads or sewn upon gar ments. About 1285 a guild of gem-cutters was established in Paris, and from that time the art of the lapidary has steadily advanced.
No modern art depends more upon the skill or' the workman. Although power has been ap plied to some of the machinery employed, yet the tools used are of the simplest nature. But the greatest knowledge and dexterity are re quired to manipulate these instruments, as a stone might be ruined by one careless stroke. Not only experience and skill, but a knowledge of optics, physics, mineralogy, and crystallog raphy, is necessary for the execution of high grade work. In earlier times the greatest pos sible size of the gene was the principal end sought by the lapidary, hut now such considerations as flawless structure, symmetrical form. and perfect
coloring are of equal importance. and to secure these the size of the gem is often sacritieed.
The first step in lapidary work is to cement the gem upon an ebony or ivory holder about the length and half the diameter of an ordinary lead pencil. The facets are then cut upon a copper disk, surfaced with diamond-powder. and rotated ley a hand-turned crank. Close to the wheel there is a cutting-rest in the form of an inverted cone. having little notches in it from top to bottom. in which the end of the gem-holder can be securely placed. thus insuring a perfectly flat cut at any desired angle. After being cut. each facet is polished by means of a revolving wheel upon which some polishing material. as emery or rotten-stone, is spread. This wheel is usually run by an electric motor, and made of the material hest suited to the quality of the stone to be polished. For a very soft -tone, like the opal or turquoise, a flannel-covered wooden wheel might lie used.
Gems arc carved by means of a lathe. with tiny wheels or disks, whose edges are primed with diamond-dust. When a stone is to be di vided, a small, thin disk of tin is used for cut ting, operated on the principle of a circular saw. For diamonds a different method of cutting and polishing is employed. See DIAMOND,