A Modern Double Rosette

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

Few Diamond Rosettes have been preserved, but I have managed to examine most of the surviving examples in great detail. The one in the pendant kept in the Grϋnes Gewölbe in Dresden was exhibited in Helsinki in the late 1960s, and inspired a large reproduction—12cm in diameter—in acrylic plastic. This reproduction was symmetrized according to what seemed, from a study of most of the surviving Double Rosettes, to be ideal proportions. It was then sent to a skilled cutter of fancy shapes, who was asked to produce the necessary components in high grade, precision cut diamonds.

Various problems faced the cutter. The first was to find enough flawless fine white rough in the right sizes and shapes. The cutter then had to find the grain in each little piece, and if the grain turned out to be unsuitable, the piece had to be rejected and a new piece found. It took six months for the job to be completed. The finished diamonds, together with a large bill, were accompanied by a firm refusal ever to repeat the task. To avoid tarnishing the metal and to enable the diamonds to be kept clean with a small brush and suitable fluid, it was decided to make the mounting of platinum and the setting open. The work of setting the stone proved to be immensely difficult and took a highly skilled and experienced master setter a whole week. How much simpler it must have been when the diamonds were first set in a bed of pitch!

The light effects of this diamond Rosette are spectacular, because the gems are clean. It seems that the reason that the slightest soiling ruins the extraordinary and subtle beauty of a diamond Rosette is because the crown and pavilion angles are so near the critical angles for reflection and refraction. When the experiment was made of soiling the stones of this jewel with grease and dirt, the magnificent light effects were almost completely lost.

From the models in acrylic plastic it can be seen how the narrow central facets of the lozenge-shaped components could be mistaken for fissures between the stones. Mielich and other artists may have been misled in this way into depicting Double Rosettes with one shape of stone only. They also often confused light and shadow. In fact, they not infrequently depicted cuts which, for one reason or another, could not possibly have existed. In his book, Gregorietti reproduces a detail of Lucrezia Panciatichi’s pendant containing a ten-petalled Rosette. The artist, Agnolo Bronzino, has made the same mistake as Mielich, since this must have been a Double Rosette with twenty stones—ten each of two different cuts.