The normally used plural of the Italian term for hardstone (pietra dura). Stones such as agate, chalcedony, jasper, and lapis lazuli have been used for small decorative objects since early times. In late Renaissance Italy, particularly in Milan and in the Grand Ducal workshop at Florence, large bowls, ewers, and vases of elaborate Mannerist design were made of such stones set into gold and enamel mounts. Italian craftsmen also produced similar work for the court of Rudolf II in Prague. From around this time also dates the first use of mosaics of hardstones for the decoration of cabinets, table-tops, altar-frontals, etc.