Pietra Dure (or pietra dura) is an Italian term for a method of inlaying coloured stones or gems into a stone base. It has been described as stone marquetry. The surrounding base in which the coloured stones are inlaid is usually black marble, though was sometimes ebony. Pietra dure first appeared in Rome in the 16th century but the craft became centred in Florence and in Naples to a lesser extent. In the 17th century, the craft spread to India where it became known as Parchin Kari.
In 1588, Grand Duke Ferdinando I de’Medici established a court laboratory which specialised in semi-precious mosaics and inlays. A common theme of these inlay pictures was flowers, sometimes with birds and fruit. As well as jewellery, pietra dure was used to decorate small boxes, chests, picture frames and tables. In the 17th and 18th centuries, the colours used were strong and intense, and the pieces had ornate gold and gilded Rococo frames.
During the mid-19th century, the stones inlaid were often lighter and more delicate, though flowers were still the common theme.
In Italy the technique is also called commesso, meaning ‘fitted together’ and ‘pietre dure’ refer to the hard stones used in the technique. As mentioned, the technique and effect is similar to wood marquetry. As well, pietra dure is similar to the older technique of mosaic but differs from it in that, micromosiacs use glass tiles of roughly the same shape to make up an image while pietra dure uses hard stones cut into the shape required, say, a leaf or flower.
The stones used in pietra dure work are hard, between 6 to 10 on the Mohs scale of hardness so that they can be cut without breaking. Commonly used stones are coloured marble, as well as gemstones like quartz, chalcedony, agate, jasper and porphyry. On rare occasions, gemstones such as emerald, ruby and sapphire were used.
The coloured stones are cut into varying shapes, depending on the picture being created, of roughly the same thickness. Then the shape of the design is cut out of the backing stone, the various components are inserted into the cut out shape and glued in, with any gaps filled with black gesso. The picture is then polished to ensure it is smooth and also waxed.
There is a museum in Florence, the Opificio delle Pietre Dure, which has a beautiful display of pietra dure work. Not so much jewellery but beautiful furniture and other objects.