Aquamarine and diamond ring, circa 1920. Aquamarine, alongside its sister stone emerald, is a variety of the mineral beryl. It owes its pale blue colour to iron impurities, and it’s this colour which has given the stone its historic association with water and the sea. Thought to protect people as they travelled across the sea, aquamarine has long been held to have calming and talismanic properties. Its large crystals make it a perfect fit for step-cuts, which meant it fit beautifully with Art Deco designs of the 1920s and 30s, finding particularly favour with the jewellers Cartier. This sky-blue aquamarine is cut in the classic emerald cut, and manages to balance substantial size with wearability. Its simple, scrolling mount fits the stone beautifully, and dates it to this classic, timelessly stylish era of jewellery design. The birthstone for March, this ring would be perfect as a birthday gift for anyone born during this early spring month, or would make an excellent choice as an engagement or cocktail ring.