About the Proportions and Shapes of Well Cut Diamonds

A properly cut diamond should have fifty-eight facets if regularly cut, and fifty-nine if cut as a patented polished girdle. One third of its size should be above the girdle and two thirds below, and the table should be two fifths the diameter of the stone. These are the correct proportions to secure the greatest brilliancy. A stone cut too deep (that is, too thick) lacks brilliancy, and one too shallow becomes flat in its effect and in the trade is termed a Fish-eye. In the cutting of the finest diamonds much consideration is now given to the girdle, while on the other hand many ordinary stones are cut with thick, rough girdles, which results in more weight being left in the stone and less expense to manufacture per carat, consequently a lower price to the customer by the carat. But it must be remembered that a poorly cut stone will not look as large as a stone of slightly less weight, if the latter is well cut.

Fine diamonds, especially those of considerable size, are cut into drop shapes, navettes or marquise shape, square cut or emerald cut, square cut with steps, and oval, the last being cut like a round brilliant, but of oval shape. Small pieces from the processes of cleaving and sawing diamonds are generally rose cut, with flat back. It is due probably to this fact that the rose-cut stones come from the fragments that they are commonly termed chips. In the old days of cutting many of the famous stones were rose cut, having when properly cut twenty-four facets. A correctly proportioned rose should be one half its diameter in thickness. Smaller and poorer roses have twelve facets.