Ametrine: A Blend of Amethyst and Citrine

Ametrine is a naturally occurring variety of quartz that is a bicolor gemstone, displaying bands of both amethyst purple and citrine yellow. Ametrine is a relatively rare gemstone, and the finest specimens are highly prized by collectors and jewelry lovers, ametrine occurs naturally only at the Anahí Mine in the Sandoval Province of eastern Bolivia.

Ametrine is composed of silicon dioxide (SiO₂ ) and it is a tectosilicate, which means it has a silicate framework linked together through shared oxygen atoms.

Rough Ametrine from Bolivia. Credit: GoldenHourMinerals

Ametrine is a mix of both Ametrine and Citrine producing a mixture of purple and yellow/orange crystal colours. It is produced under such exceptional and improbable conditions, requiring a perfect combination of iron presence and differing temperatures within a very confined area, that it has occurred only once that we know of, in only one known place in the world: Santa Cruz, Bolivia.

The Anahí mine is the one and only bolivianite mine known to exist anywhere on Earth. The mineralization is found in the northern part of a hill formed by limestones and dolomites, and has been generated by silicification of the limestones belonging to the Murcielago Group, deposited in the Precambrian, between 500 and 900 million years ago. Ametrine crystals are found in hydrothermal breccias.

Rough Ametrine Crystal from Bolivia

The Anahi ametrine crystals range in size from 10 to 30 cm in length and 4 to 12 cm in diameter. When sliced and polished, the interior of the crystals show the typical color zoning. The amethyst and citrine zones run from top to bottom, parallel to the crystal’s c-axis.

Ametrine in the low price segment may stem from synthetic material. Green-yellow or golden-blue ametrine does not exist naturally. This gem only exists in Bolivia, it comes from the Ricón del Tigre area, from the Anahí mine.

Here are some additional facts about ametrine:

• The color zoning in ametrine is caused by a temperature gradient across the crystal during its formation.
• Ametrine is often cut into cabochons or other shapes that showcase its unique appearance.
• Ametrine is a popular choice for jewelry, especially earrings, necklaces, and bracelets.