As the name of ametrine shows, it is a natural mixture of amethyst and citrine. It is also known on the name bolivianite, because its main locality is the Anahi Mine in Bolivia where the most of the ametrines origin from. Its formation is roughly the same as the amethyst’s. Due to the different oxidation of the iron in the crystal it got its colors. There are treated and synthetic ones on the market. Beside its main locality, Bolivia it can be found in Brazil.