Natural pearls are the product of oysters, created in response to an irritant in the shell. The irritant, often nothing more than a grain of sand, it is coated over time with layer upon layer of a substance known as nacre, creating a shimmering and lustrous surface with a subtle iridescence. Natural pearls are the birthstone for june, and extremely rare - by their very nature they can neither be farmed or mined, and each find is simply a stroke of good fortune. Consequently natural pearls have been treasured for millennia, synonymous with power and opulence, and worn by some of the most captivating and powerful women in history, including Cleopatra, Elizabeth I, Catherine de Medici and Marie Antoinette, as well as 20th century icons such as Elizabeth Taylor and Jacqueline Kennedy. The best natural pearls show a highly lustrous and smooth surface, free from imperfections, combined with a regular and even shape. While natural pearls have adorned both women and men for generations, as organic gemstones, pearls are relatively soft, and more suited to occasional rather than everyday wear. To keep their natural lustre intact, they are also best kept away from chemicals such as perfumes, which can affect the surface.