Amethyst and Diamond Ring. Amethyst is a variety of quartz in a beautiful, rich shade of purple - the result of exposure to natural radiation in the earth. This colour gave it its long-standing association with wine, which has persisted since the ancient world. Its name derives from Greek, meaning ‘to be sober’, and it was thought to guard against drunkenness. This beautiful circular-cut amethyst is set within a delicate border of rose-cut diamonds, mounted in traditional silver and gold, contrast offsetting the amethyst’s gorgeous, rich violet colour.