The Cuboid Cut

(via Diamond Cuts in Historic Jewelry:1381-1910) Herbert Tillander writes:

The term Cuboid Cut has been given to diamonds which have all the six planes of a cube, even though they may contain combinations of the octahedron and the dodecahedron as well. Growth like this in the crystal was perhaps what first inspired cutters to produce these fancy shapes, though later Cuboid Cuts were probably also fashioned from rounded or oval dodecahedrons.

Depending on the outline of the rough, the girdle outline of a Cuboid Cut is either a regular or a slightly elongated octagon with four main square or rectangular facets in the crown sloping towards the girdle from the table. These facets, which form a cross, are separated from each other by triangular facets. The girdle, composed of eight high vertical facets, is very thick. The pavilion design is similar to that of one in a normal Table Cut. The culet is usually small and the same shape as the table. The table, the culet and four of the girdle facets form the cubic planes. The main facets correspond more or less to dodecahedral faces, and the triangular facets to octahedral faces.

Once they had achieved this original shape with very little loss of weight, some cutters ( such as the maker of the cuboid gem on the Burgundian Court Goblet) found that they had also, though probably by chance, produced a diamond of exceptional brilliance—such brilliance, in fact, that when I first saw the diamond on the Burgundian Goblet in Vienna, I thought it must be a modern replacement. Later, when I was allowed to study all the diamonds on the goblet, I was able to assure myself that this was indeed the original diamond and that it had never been replaced. The Cuboid Cut apparently became more popular than the Burgundian Point Cut in the fashioning of dodecahedral rough, but it did not survive nor evolve into any other design.

Hartley (1968) explained how to fashion, from synthetics, a Cross Brilliant. This is a design circular in outline, but with a square table—very similar, in fact, to the old Cuboid Cut. Hartley described it as being ‘very simple cut, but it has a surprising amount of brilliance’, and said that the table facet must be perfectly square adn 25-26 percent of the width of the stone. Perhaps the old Cuboid Cut has been revived!