Semi-precious stone is a traditional term for gemstones and ornamental minerals other than the four classed as precious: diamond, ruby, sapphire and emerald. It includes agate, amethyst, carnelian, chalcedony, garnet, jasper, lapis lazuli, malachite, onyx, rock crystal, turquoise and many others. Modern gemmologists often avoid the distinction, since some so-called semi-precious stones can be rarer and more valuable than precious ones.
Semi-precious stones have been carved, polished and set since antiquity, used for seals, cameos, intaglios, beads, boxes and vessels. In Renaissance Florence, the technique of pietra dura used shaped pieces of coloured stone to create pictorial inlays for tabletops and cabinets, and later workshops continued the tradition. Russian craftsmen became famous for malachite and lapis lazuli veneers on vases and furniture, while Victorian Scotland produced distinctive agate jewellery set in silver. Grand Tour visitors to Italy bought specimen tabletops and obelisks inlaid with many varieties of stone. Collectors consider the quality and colour of the stone, the skill of cutting and setting, and condition, since chips, cracks and replaced stones reduce value. Some stones are dyed or imitated in glass, so careful examination is wise. Polished stone objects bring colour and a sense of natural richness to any display.
