Amethyst is a stone of spiritual protection and purification, cleansing one's energy field of negative  influences and attachments, and creating a resonant shield of spiritual light around the body. It acts as a barrier against lower energies, psychic attack geopathic stress and unhealthy environments. It's often the best gem to calm and relax the nerves. 
Amethyst is connected to the third eye and crown chakras. Amethyst's reddish-purple to purple hue has long been associated with tranquility, purification, and energy.