Jewels have always been morally ambiguous. The Gospel of Matthew might have compared the kingdom of heaven to a ‘pearl of great price’, but jewels continue to signify vanity, indulgence and sexual availability. The bijoux indiscrets of Diderot’s novel were gossiping pudenda, and pearls have always been associated with female anatomy. Jewellery is designed for consumption by others. It draws attention and, at its most effective, enhances the wearer. Jean-André Rouquet, an eighteenth-century French miniaturist, sounds strikingly contemporary when writing of the power of gems: ‘The brilliancy and value of jewels is one of the surest means of adding something to the importance of our being; they proclaim us from afar; they extend, as it were, the limits of our existence.’ Yet the more magnificent the jewellery, the more threatening it can be. The wearer’s ugliness might contrast unfavourably with the sparkle of the stones (as with Cinderella’s sisters), or her personality be lost in the dazzle.