A Rare GemAmetrine is an unusual quartz formation in which both amethyst and citrine occur together in the same crystal structure. Although quartz is the most abundant single mineral on earth – naturally formed ametrine is one of its rarest. The world’s best known source of ametrine is the Anahí mine, in southeastern Bolivia. In recognition of Bolivia’s importance as the only source of these unusual gems, they have become widely known as Bolivianite.
History Varieties of quartz have been used as gemstones and ornamental objects for thousands of years. Ametrine has only been readily available since 1980, when crystals from Bolivia’s Anahí mine were first commercialized. Before this, Ametrine was considered to be extremely rare and carried the name trystine or golden amethyst.  Mining and processing Gemstone mining techniques need to be quite different from traditional mining operations. Mining operations take place in underground tunnels that follow the irregular veins of mineral rock. No explosives are employed when quartz structures are reached, and extraction of gem crystals is carried out painstakingly by hand. Crystals are carefully graded according to color depth and size. Natural flaws and fractures prevent much of the quartz from being cut into gem quality stones. A number of other crystal ornaments and products are made from this material, where the imperfections add characteristic qualities to the pieces. Only carefully selected quartz is used for the cutting of gemstones, and quality control at every stage of production ensures a flawless and uniform cut stone.  Geology and chemistry Quartz occurs in a wide variety of rocks. Ametrine is a macro-crystalline variety of quartz and is readily recognized by its colors, hardness, glassy luster, and lack of cleavage properties. For ametrine to occur, iron impurities in different oxidation states (Fe4+ and Fe3+) must enter the crystal structure in a number of different places during its formation The delicate balance between temperature, pressure and the chemical environment of the quartz all had to be maintained for a considerable period of time while crystallization preceded the reason for ametrine’s rarity. 
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