Amethyst Jewelry

Where the name comes from: Greek translated as a-methystos - not-intoxicated, it was believed that the stone was a protection against drunkenness, it was worn as a gem and used to make drinking vessels from.
Where the stones come from: Widespread, most commercial forms come from Brazil, Uruguay or Madagascar.
Chemistry: Silicon dioxide, SiO₂ - Amethyst is a variety of quartz with 10-100's parts per million of iron impurities which give it the color.
Colors: Purple violet to reddish.
...and another thing: Up to the 18th century amethyst was one of the most valuable gemstones along with diamond, sapphire, ruby and emerald, the discovery of large deposits in Brazil  in particular reduced its value greatly.
 

Prices correct at time of writing - subject to change

Kate Spade New York Molten Glass Studs Women's Earring Light Amethyst, Cubic Zirconia/Glass On sale - now $100 - was $58