It is in consequence of this lamellar structure that pearl-shells admit of being split into laminæ for the handles of knives, for counters, and for inlaying. Splitting, however, is liable to spoil the shell, and is therefore avoided as much as possible. The different parts of the shell are selected as near as possible to suit the required purposes, and the excess of thickness is got rid of at the grindstone. In preparing the rough pearl-shell, the square and angular pieces are cut out with the ordinary brass-back saw, and the circular pieces, such as those for buttons, with the annular or crown-saw, fixed upon a lathe-mandrel. The pieces are next ground flat upon a wet grindstone, the edge of which is turned with a number of grooves, the ridges of which are less liable to be clogged than the entire surface, and hence grind more quickly. If the stone be wetted with soap and water, it is less liable to be clogged. The pieces are finished on the flat side of the stone, and are then ready for inlaying, engraving, polishing, &c. Cylindrical pieces are cut out of the thick part of the shell, near the hinge, and are rounded on the grindstone preparatory to being turned in the lathe. Counters, silk-winders, &c., are smoothed with Trent sand or pumice-stone and water on a buff-wheel or hand-polisher, and are finished with rotten-stone moistened with sulphuric acid, which develops finely the striated structure of the shell. For inlaid works, the surface is made flat by filing and scraping; then pumice-stone is used, and after this putty-powder, both on buff-sticks with water; and the final polish is given with rotten-stone and sulphuric acid, unless tortoise-shell, or some other substance liable to be injuriously affected by the acid, be present in the inlay. In turned works, fine emery-paper, rotten-stone and acid or oil are used. The pearl handles for razors are slightly riveted together in pairs, then _scraped_, _sand-buffed_ on the wheel with Trent sand and water; thirdly, _gloss-buffed_ on the wheel with rotten-stone and oil, or sometimes with dry chalk rubbed on the same wheel; and fourthly, they are _handed up_, or polished with dry rotten-stone and the naked hand.