Stunning as a single pop of colour on a statement brooch, or as a multi-stone piece that showcases the stone’s iridescence, the opal equally conveys its strength alone and in numbers. While October’s birthstone is also the tourmaline, we wanted to highlight the opal for its wide-ranging spectrum of shades, from a matte pink or white, to a fiery red or blue. To see the many hues of this magical birthstone, click through the slideshow and discover the best of both past and upcoming opals at Sotheby’s.