Ametrine in triple A, with two sides (rough and polished side) on a base, from Anahi-Bolivia.

Ametrine, also known as trystine or by its trade name as bolivianite, is a naturally occurring variety of quartz. It is a mix of amethyst and citrine with zones of purple and yellow or orange. Almost all commercially available ametrine is mined in Bolivia, but there are deposits in Brazil and India that are exploited. The colour of the zones visible in ametrine is due to the different oxidation states of iron in the crystal. The different oxidation states occur as a result of a temperature gradient across the crystal as it is formed. Artificial ametrine can be created by differential heat treatment of amethyst. Legend has it that ametrine was first introduced to Europe by a conquistador as a gift to the Spanish queen, who had a mine in Bolivia as a dowry when he married a princess from the indigenous Ayoreos tribe. We can assume that most low-priced ametrine originates from synthetic material. Since 1994, a Russian laboratory has perfected the industrial production of two-tone quartz crystals that are later irradiated to bring out the typical ametrine colours. Green-yellow or gold-blue ametrine does not occur naturally.