Opal, October’s birthstone, is a captivating gemstone because of its unique optical characteristics. Opals often exhibit a spectrum of colors called “play-of-color,” when viewed from various directions. The Roman naturalist, Pliny the Elder, referred to opal’s play-of-color in the 1st century AD when he wrote: “For in them you shall see the living fire of ruby, the glorious purple of the amethyst, the sea-green of the emerald, all glittering together in an incredible mixture of light.” (more…)