A beautiful opal can cast a spell on its admirer. Whether it is a red-hot fire opal from central Mexico or a complexly patterned black opal from southeastern Australia’s famed Lightning Ridge, the stone’s enigmatic combination of glittering light and profound darkness calls to gem lovers the world over. Each opal is an organic work of art, formed in the earth over millions of years from the evaporated mixture of silicon dioxide and water. The most coveted of these gemstones possess what is referred to as “a play of color,” which is when tiny specks of silica capture light and reflect it back, creating a hypnotic sparkle. Here, we have chosen five designers who are honing one of nature’s most vibrant works of art.