Ametrine, Anahi Mine, Bolivia
The best known source in the world for ametrine is the Anahi Mine in the La Gaiba District, Sandoval Province, Santa Cruz Province, Bolivia. The ametrine crystals from this mine are unique: the color is a combination of rich, deep royal purple amethyst with golden yellow citrine.
The Anahi Mine has been known for hundreds of years. It is located in the midst of the rainforest zone, near the Pantanal wetlands on the Bolivia-Brazil border. The story is that the mine first became famous in the seventeenth century when a Spanish conquistador received it as a dowry when he married an Ayoreos princess named Anahi. Ametrine crystals were first introduced to Europe through the conquistadors’ gifts to the Spanish queen.
Ametrine, Anahi Mine, Bolivia
However, ametrine has only been available on the market in any quantity since about 1980. My friend Bob Jackson, of Spruce Claim, WA fame, was hired as the mine geologist by mine operators Minerales y Metales del Orient around 1990. The mine operated for about 10 years, exploiting the veins of ametrine for both the specimen and cut stone markets. In 2001, Bob was contacted by the mine operators. It was an emergency: they needed Bob to relocate the ametrine vein, which the miners had somehow managed to lose in the complex of mine shafts and tunnels! He flew down to Bolivia, but unfortunately, he was not able to be of much help. The vein had disappeared.
Ametrine, Anahi Mine, Bolivia
This led to a prolonged dry spell, with some gem rough production, but very few collector quality crystals. Finally, in 2009, miners at the Anahi Mine hit a new vein which produced high-quality crystals of ametrine for the first time in decades. We are lucky enough to have had access to the first cherry-picked lot from the new find.
Ametrine is a variety of quartz that contains both amethyst and citrine sectors in the same crystal. Both amethyst and citrine are colored by small amounts of iron (approx. 40 parts per million). Amethyst color develops when iron-containing quartz is exposed to ionizing radiation.
Ametrine, Anahi Mine, Bolivia
The color zones visible within ametrine are referred to as sectoral zoning. They are the result of 2 different factors: One is differing oxidation states of iron which occur inside the crystal due to temperature differences across the crystal during its formation. The second is the selective distribution of the naturally occurring iron coloring agent in the different zones of growth.
Ametrine, Anahi Mine, Bolivia
The ametrine at the Anahi Mine occurs in veins in a dolomitic limestone. Crystals of Bolivian ametrine range from 10 cm to 30 cm in length, with diameters ranging from 4 to 12 cm. The crystals almost always have a rough exterior, and are lacking the smooth sides and prism termination characteristic of quartz crystals. On close examination, the “rough” sides are made up of alternating vertical bands of shiny well-crystallized areas and irregular but very smooth uncrystallized sections. Occasionally, the crystals will have rough quartz terminations and, rarely, a vaguely 6-sided shape.
Ametrine, Anahi Mine, Bolivia
The interior of the crystals, when sliced and polished, show the typical sectoral zoning. The amethyst and citrine sectors run straight from top to bottom, parallel to the crystal’s c-axis, which is very different from an amethyst-on-top-of-citrine scepter or a gradual transition often seen in smoky-amethyst specimen.
Please click here to visit the Ametrine gallery on our website.
