Soft stones, as Opals, Peridots, &c. are polished on mills covered with cloth, and oxide of tin is used with a little water, instead of rotten-stone.
Gems that require nicety in cutting, whether in steps or brilliant, should be given to an experienced workman. The operation is commenced by holding the stone between the fingers until it is rubbed down into the shape required, first forming the table, next the bizel and girdle, and lastly the collet-side, This done, the stone is cemented to a round stick, four or five inches in length. The ribs and facets are formed by holding the stick in an inclined position on the mill, and supporting the other end in a notch on the gin-peg: this instrument is an upright peg, fixed in the bench by the side of the mill, containing holes or notches, one above another, to receive the
