Amethyst is a beautiful form of quartz crystal and its color ranges from pale lavender to the darkest shade of violet. This gemstone has many symbolic associations with both ancient and modern times. The most well-known story is that of the Roman god of wine, Baccus, and the gemstone amethyst.
The following quote was shared by the International Gem Society. The quote itself comes from the French poet, Rémy Belleau who created this story in 1576 as part of a poem on gemstone beliefs.
"Long ago, a beautiful maiden was on her way to worship at the Temple of Diana. However, she had the misfortune of crossing paths with the god of wine, Bacchus. Angered since he’d just suffered some slight, he’d vowed to take revenge on the next person he met. He spied the maid and unleashed his two guardian tigers upon her. As the great beasts bounded towards the hapless lass, the goddess Diana intervened. To spare her such a terrible fate, she turned her into a pure, clear stone.
Immediately, remorse seized Bacchus. To atone for his actions, he poured his wine over the stone, staining the crystal a deep, violet hue. And so, the maiden Amethyst lent her name to the crystal."
The idea that Amethyst helps one to stay sober, I believe, comes from a much older time. Its very name comes from the Ancient Greeks. Amethystos means "not drunk" in Ancient Greek and they believed that you could drink all night and remain sober if you had an amethyst in your mouth or on your person--most often in the form of jewelry.
For obvious reasons, I don't recommend trying to drink all night with an amethyst in your mouth. If you do want to drink all night, I suggest you also drink water. That's how I do it and I've never had a hangover in my life.