Answer: Amethyst

Many a museum-goer over the years has been puzzled over the inclusion of amethyst in royal and religious artifacts. Why would the artisans of past ages have included amethyst in so many of their creations when it’s such a cheap and abundant stone, merely quartz with a purple hue?

Historically, amethyst wasn’t cheap and abundant, however, and was considered one of the cardinal, or precious, gemstones right along with diamonds, emeralds, sapphires, and rubies. That all changed in the 18th century when enormous deposits of amethyst were discovered in Brazil. The discovery permanently demoted amethyst to the rank of semi-precious where it has sat ever since with gemstones like topaz and tourmaline.