Black pearls have always been admired for their beauty and rarity. To call them "black" is slightly misleading, as in fact, being produced by nature, they are all a little different and vary from dark grey/black to aubergine with wonderful green or purple overtones. The oyster producing most of the black pearls, that are found off of the Mexican coast, is the Pinctada Margaritifera, which is best known for its black, dark grey and gun metal coloured pearls. The degree of "blackness" is due, in part, to the colour of the shell as well as the black organic substance in the pearl.
It was not until the second half of the nineteenth century that black pearls grew in popularity. This was principally due to Empress Eugnie, wife of Napoleon III, who developed a taste for these exotic gems. In the sale of her jewellery at Christie's in 1872, a black pearl necklace sold for 4,000 ($20,000), a huge sum in those days. Very few black pearl necklaces have been sold in recent years, the most famous being the three-row Nina Dyer necklace, that consisted of 151 pearls and sold at Christie's Geneva in November 1997 for $913,000.