Amethyst:

Amethyst contains such very rich color that one can see why it is called the color of kings. It is February’s birthstone, a "winter "color. that is supposedly imbued with supernatural powers. It brings luck, ensures constancy and protects against homesickness. In Greek times it was worn as an amulet as protections against drunkedness. The best amethyst deposits are in Brazil, Uruguay, and the Malagasy Republic.