Italian circa 1880. 40mm by 33mm. Pietre dure is the art-historical term for the technique of using small, exquisitely cut and fitted, highly-polished colored stones to create what amounts to a painting in stone. It is considered a decorative art. The stonework, after the work is assembled loosely, is glued stone-by-stone to a substrate after having previously been "sliced and cut in different shape sections; and then assembled together so precisely that the contact between each section was practically invisible".[1] Stability was achieved by grooving the undersides of the stones so that they interlocked, rather much like a jigsaw puzzle, with everything held tautly in place by an encircling 'frame'. Many different colored stones, particularly marbles, were used, along with semiprecious, and even precious stones. It first appears in Rome in the 1500s[2] but reaches its full maturity in Florence. Pietre dure is an Italian plural meaning hard rocks, or perhaps better durable stone and this is the preferred term; the singular pietre dura is also encountered. The English term "Florentine mosaic" is sometimes also encountered, as is "micromosaic", but these are disparaged, often as terms developed by the tourist industry. As an artistic medium, it descends from Byzantine mosaics, especially their predilection for incorporating semiprecious and precious stones into the work. It is distinct from mosaic, however, in that first, the stones are not cemented together with grout, and second, for the fact that the works in pietre dure are generally portable. .

SOLD