Ametrine is a naturally occurring variety of quartz that combines both Amethyst and Citrine. Color zones of violet amethyst to golden yellow citrine are visible within Ametrine , and are due to differing oxidation states of iron within the crystal. The different oxidation states occur due to there being a temperature gradient across the crystal during its formation. Almost all Ametrine comes from Bolivia, although there are a few small pockets in India and Brazil. It is believed in stone folklore to stimulate the intellect and banish negative energy.