Amethyst is a member of the Quartz family. Back in the day, Amethyst was used for curing alcoholism and intoxication. Amethyst was traditionally worn as a talisman for believers to keep a sober mindset. Nowadays though Amethyst is a good stone for protection. Especially when placed up against clear quartz as it amplifies the energy between either crystals.
Amethyst is also used as a clearing stone to stop it from absorbing up too much negativity especially if the stone itself has collected it for you. If placed on the opposite door to the entrance of the room that you are residing in it can be used to draw in Abundance and Material Wealth if with working with Vera Cruz Amethyst. Elestial Spirit Amethyst can also clear auras and energies lingering within one's aura if asked to do so.
It is also a good stone to protect up against night terrors and unpleasant dreams. If ever unsure of working with the stone you can ask it to sign you a sign of confirmation to say its heard your request.