Page:Popular Science Monthly Volume 8.djvu/220

208 of the gem, and form table diamonds by adroitly striking along one of the planes with a sharp-edged tool, thereby separating the layers, as slate is rifted by the miner. This operation, which appears so simple, really requires considerable skill, and much of that acquired instinct or tact which is best exhibited by our Western Indians, who chip, with marvelous rapidity and certainty, a glass-bottle into symmetrical arrow-heads.

The workman at a glance ascertains the direction of the laminæ, and with another diamond cuts a notch at the point where he would begin operations. In this notch he places the edge of his blunt steel knife, and, by tapping the back of it with a light iron rod, he splits the diamond with perfect ease. In reducing the natural diamond to a regular form, much of its substance is lost, and sometimes as much as one-half the weight of the stone. The amount of loss, however, depends

greatly on the natural form of the crystal. Perfect octahedrons lose but one-fifth of their weight when fashioned into brilliants, but rhombohedrons lose over one-third on taking the same form. The following figures will give some notion of the loss:

The process of cutting diamonds of large size is always attended with risk, and is necessarily a costly operation. The Regent cost for cutting $25,000, and occupied two years' time. The Star of the South occupied only ninety days, and the Koh-i-noor only thirty-eight working-days. This great feat in diamond-cutting was performed by the