Trihedrally Faceted Gothic Roses

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

This term is used for a design in which each basic triangular face has been replaced by a flat three-sided pyramid—that is, by three triangular faces raised to a low point. This is one of the very oldest faceting patterns, originally applied only a triangular rough. As in the case of six-facet Rose, the crystal shape which inspired the early cutters was likely to have been a cleavage with three natural faces. Such roughs may have been cleaved accidentally off a well developed trisoctaheral face, or they may have been a corner of a cuboid crystal.

Once the triangular rough had been fashioned into the simple pattern with three facets, an optical illusion caused by internal reflection made the Chiffre look as though it had nine facets, and this may have inspired cutters to apply trihedral facetings on the faces of rounded octahedrons, which was much easier to achieve than perfect plane facets. The subdividing of often numerous triangular faces into small facets was considered attractive and provided a popular alternative to Table Cuts, with their large, severe facets and strict geometry. Trihedral faceting was soon applied to flat-bottomed diamonds of every possible outline. It was most popular for angular shapes, but was also fairly common for diamonds with rounded outlines.

Not all diamonds with trihedral faceting are flatblacks. Some have pavilions of varying depths, difficult to distinguish in the closed settings of historical jewels and almost impossible to see in photographs. Most pavilion based diamonds (at least until the middle of the seventeenth century) were fashioned into Burgundian Point Cuts or Pointed Star Cuts.

In addition to Chiffres and six facet Roses, the Gothic Rose Cut included flat-bottomed diamonds of every conceivable outline, produced by economically minded cutters striving to save weight while achieving certain decorative effects as well as maximum display. Facets were applied at random, though usually in combinations of triangular facets. Perfect symmetry existed in the minds of artisans and designers only as an ideal and not necessarily as a practical goal.

The cube or hexoctahedron, is extremely rare in gem quality stones, but cube faces appear frequently in crystal combinations. The corners of a cubic formation can easily be cleaved off and produce excellent forms for further fashioning into Rose Cuts.

The kite-shaped diamond in the Dresden Cross Pendant clearly shows its trihedral faceting partly because of its unusual height (at the blunt end the face edge stands at an angle of 45º to the flat bottom) which makes it an outstanding feature. The soiled and damaged ancient foiling makes it impossible to analyze color or clarity adequately. The diamond is now yellowish and inclusions can be seen even with the naked eye. The choice of such a stone indicates that the jeweler was more interested in creating something beautiful than in producing a valuable piece of jewelry.