Once Cleopatra’s alleged favourite gemstone, the emerald continues to make a glamorous impression on everyone from royals to the red carpet’s best dressed. Beloved for their rich, exotic colour, emeralds are a bluish-green variety of the mineral beryl. When chromium, vanadium and iron are present in beryl, emeralds form, and the varying presence of these three elements results in a range of colours – chromium and vanadium lead to intense green, while iron produces a blue tint. If the stone’s hue is too yellow or blue, it is not an emerald but rather a variety of beryl, which makes highly transparent and vividly saturated green emeralds extremely valuable. In honour of May’s birthstone, we selected fifteen extraordinary emerald lots from our upcoming jewellery and watches sales around the world.