Amethyst is a royal stone. Worn by many kings, queens, priests and other leaders for its mystical protection and ability to keep one attuned and focused. Having this beautiful crystal on or near you, raises your vibration, and stimulates the third eye, crown and etheric chakras, opening you up to the higher realms and cosmos, and guiding one through spiritual awakenings. This crystal can guides one through astral realms, and enlighten one to deep cosmic knowledge. Amethyst is also a protective stone, transmuting and dispelling negative energies, and clearing the energy of any space, including your own aura. It is great for reiki, since this crystal can aid the practitioner in opening themselves to the higher spiritual planes, and simultaneously clearing the clients energy of unwanted vibrations and frequency.
Amethyst is also great for anyone suffering from addictions, since this crystal helps the mind and body overcome toxicity and influence. The word itself comes from the Greek word 'ametusthos', which translates to 'not intoxicated'.
P.S. Another fun fact, Amethyst had commonly been worth as much as diamonds throughout points in history.