Amethyst:

Amethyst is a meditative and calming stone which works in the emotional, spiritual, and physical planes to provide calm, balance, patience, and peace.

Amethyst is used as beneficial when dealing with legal problems and money issues, which can lead to prosperity and abundance, though it is not the best known prosperity stone.

In the psychic and spiritual realms, amethyst is an excellent all-purpose stone that can increase spirituality and enhance intuition and psychic powers of all kinds. It does this by making a clear connection between the earth plane and other planes and worlds. Amethyst is also excellent for meditation and lucid dreaming. It is used to open one's channels to telepathy, past life regression, clairaudience, clairvoyance, and communication with angels. Amethyst also protects against psychic attacks, especially during spiritual work.

Amethyst is not only a psychic protection stone, but is also used to protect one from thieves, and to protects travelers. 

Emotionally, amethyst is used in crystal healing  to help heal personal losses and grief, bringing one gently past. Amethyst has a gently sedative energy that can promote peacefulness, happiness, and contentment. It also is said to bring emotional stability and inner strength. This stability and strength not only helps one hold firm in one's life, but it can enhance flexibility and cooperation. To be flexible at need is a sure sign of strength.

Amethyst is very well known -- as from the ancients -- as a sobriety stone. It has been used for millenia to prevent drunkenness, and is used to assist in getting rid of addictions to alcohol, drugs, smoking, etc, and destructive compulsive behaviors of all kinds.