gemstonesonline.org

Colored stones fashion

Posted March 24th, 2009 by admin

The fashioning of colored stones is quite a separate industry, no workshop cutting both diamonds and other precious stones. The abrasives and machinery used are different, as are also the methods. Slitting is done with metal plates or wheels of soft Swedish steel edged with diamond paste, set vertically, and rotated about horizontal spindles. For grinding and polishing, discs or laps, often of gun metal, ten to twelve inches in diameter, and set horizontally but rotated about vertical spindles, are used. Diamond or corundum powder, depending upon the hardness of the stone being ground, is used as the abrasive agent, but emery, a coarse form of corundum, is much employed in grinding the varieties of quartz and many other semi-precious stones.

Various grades of emery, known by numbers, may be obtained, the range varying from 6 to 600. The number represents the number of holes per inch in the grading sieve through which the powder has been passed. The powders are applied in the form of a paste to the metal wheels, and these vary in composition according to the material being fashioned. Pewter, copper, and leaden wheels are all used, and in these, the grains of emery are embedded by revolving the laps at speed. Almost continuous cooling by water is necessary to avoid over-heating, and this process is sometimes known as mud-lapping.