Gemstones are minerals and certain organic materials that are prized for their beauty, durability and rarity, and are cut and polished for use in jewellery and decorative objects. The traditional precious stones are diamond, ruby, sapphire and emerald, while semi-precious stones include amethyst, garnet, topaz, aquamarine, turquoise, agate and many others; pearls, amber and coral are organic gems.
Gemstones have been used for adornment since antiquity, and their treatment reflects changing technology and fashion. Early stones were often polished en cabochon, while the development of faceting led to table cuts, rose cuts and, in the eighteenth and nineteenth centuries, the old mine cut and old European cut diamonds that preceded the modern brilliant. Beyond jewellery, gemstones and hardstones were set into snuff boxes, seals, watch cases, sword hilts and pietra dura panels, and carved into cameos and intaglios. Victorian jewellery made particular use of garnets, turquoise and Scottish agates. Collectors and buyers should be aware of glass paste imitations, synthetic stones and treated gems, and important pieces are best assessed by a qualified gemmologist. The style of cutting and setting is often a useful guide to dating antique jewellery.
