Now the melancholy God protect thee, and the tailor make thy garments of changeable taffeta, for thy mind is opal. – William Shakespeare, The Twelfth Night

There is in them a softer fire than the ruby, there is the brilliant purple of the amethyst, and the sea green of the emerald – all shining together in incredible union. Some by their splendor rival the colors of the painters, others the flame of burning sulphur or of fire quickened by oil. – Pliny, about the opal

The violet of the amethyst represents the deep purple shade of the heavens… – Charles Blanc, Art in Ornament and Dress, 1875, translated from French