Ametrine, tumbled in triple A-quality (15-20 mm) 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. Differential heat treatment of amethyst can create artificial ametrine. 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. A Russian laboratory has been perfecting the industrial production of two-tone quartz crystals since 1994, which they then irradiate to bring out the typical ametrine colours. Green-yellow or gold-blue ametrine does not occur naturally.