There are a number of locations where ametrine has been known to occur naturally, but the stone is somewhat rare and there is only one place where a significant quantity of gem-grade ametrine can be found: Santa Cruz, Bolivia. With such limited provenance of high quality stones, ametrine has earned the lesser known trade name of “Bolivianite” in honour of the Bolivian ametrine deposit. The vast majority of ametrine gemstones available on the market come specifically from the Anahi Mine in La Gaiba mining district of Santa Cruz’s Ángel Sandoval province, a mine which has a history that is said to go back over 400 years.
The area of the Anahi Mine; although not easily visible, the mine entrance is in frame between the two small mountains pictured. Image: Robert Weldon/ GIA
Legend has it that the indigenous Ayoreo people of Bolivia knew about ametrine long before any European settlers, but the stone did not make its first appearance on the world stage until the 1600’s when Spanish conquistadors ventured to Bolivia. According to the stories, one of the more prominent conquistadors encountered an Ayoreo princess with whom he became quite enamoured and desired to marry. The legend says that the Spaniard received the mine as part of the dowry for his marriage to the princess, naming it “Anahi” after his new wife. Europeans thus learned of the varicoloured quartz gem now known as ametrine when specimens from the newly-acquired mine were sent back to Spain.
Knowledge of the Anahi Mine then seemed to disappear for nearly 300 years–likely because of how difficult it is to access the mine’s location, a feat that is still onerous even to this day. The first known contemporary documentation of bi-coloured quartz exhibiting both purple and yellow hues appeared in a 1925 issue of American Mineralogist, although at the time these stones were not attributed to Bolivia or any large well-mapped deposit of ametrine. During the 1960’s the Anahi Mine was rediscovered, and by the 1970’s ametrine began to enter the contemporary market in significant quantities, however there were legal restrictions to mining in Bolivia so in order to protect mining operations the global market was put under the impression that the mining of ametrine was taking place in neighboring South American countries including Brazil and Uruguay. This secretive attitude around the origin of ametrine had significant portions of the gemstone market confused. In some cases, this further fueled suspicions that the stone was not completely natural, with many voicing concerns that the colour zoning was the result of heat treating limited portions of amethyst crystals.
In the late 1980’s, the Bolivian government made changes to its mining laws and this allowed for more transparency around the source of ametrine gemstones. By this time the company Minerales y Metales del Oriente S.R.L. had obtained mining rights to a large area of land which included the site of the Anahi Mine, and after the change in Bolivian mining regulations geologists and gemologists were eventually allowed to visit the Anahi mining site to confirm the natural origins of the two-toned quartz; the work of those scientists put all doubts to rest, and ametrine was verified as a completely natural stone. Today, the Anahi Mine produces most of the world’s ametrine as well as both single/bi-coloured amethyst and single/bi-coloured yellow quartz. A short time after ametrine was scientifically verified as natural, a small mining operation began in the 1990’s approximately 50 kilometers north of the Anahi Mine in Yuruty, where a notable although quite limited supply of gem-grade ametrine was discovered; the Anahi Mine still remains the most important source of this dual-hued quartz treasure.
Ametrine continues to be a gemstone oddity that draws in onlookers with its motley colouration and seemingly improbable existence. A distinctive and idiosyncratic quartz variety, ametrine is a fantastic example of a gemstone that shows how nature can make the unreal, real.
© Yaĝé Enigmus a.k.a. Kevin Back
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