Ametrine is the name given to crystals that contain both Amethyst and Citrine. Amethyst is a purple form of Quartz and Ametrine a golden-yellow form. They develop their characteristic colors because of chemical impurities present when the Quartz crystal is forming - if the right impurities are present in the right place then both Amethyst and Citrine can form in the same crystal. Ametrine usually forms with blurred bands of purple and yellow crystal, though high quality specimens may have a dark purple base lightening to a golden yellow tip.
Ametrine is believed to concentrate the best qualities of Amethyst and Citrine. The combination of mental clarity and strength of will makes this a powerful stone for any magic user or spiritual seeker. Ametrine is often used to help defeat addictions and is an ideal crystal for that purpose, because Amethyst's powers of clear-headed abstinence and focused thought combine with Citrine's bright healing energy and ability to boost willpower. The crystal can increase your determination to be free of addiction while helping you focus on why it is so important for you to do so. A Citrine crystal is an excellent 'worry stone' to touch and play with and can help distract your thoughts when you are suffering the pain of withdrawal.