Quartz (Polished)

specimen number:
2292210

location:
Anahi Mine, Santa Cruz, Bolivia

description:

A glassy gemmy polished piece of quartz, this material often referred to as ametrine.

The Anahi mine, located in the Angel Sandoval Province of eastern Bolivia near the Brazilian border, is a world-renowned underground gemstone operation situated within a dense tropical forest environment. Geologically, the deposit is hosted within a sequence of dolomitic limestones belonging to the Precambrian Murcielago Group, where structural movement along a major fault zone created open breccias and vugs that were later filled by low-temperature hydrothermal silica solutions. Mining in the region historically dates back to the seventeenth century when the Ayoreos indigenous tribe introduced the gems to Spanish conquistadors, but modern commercial exploitation and systematic underground tunneling began in 1989 under the Minerales y Metales del Oriente company. The mine has maintained continuous mechanized underground operations and localized extraction, cementing its status as the world's primary commercial source of high-grade amethyst and bicolor quartz well into the 2020s.

Ametrine is a rare bicolor variety of quartz that exhibits both purple amethyst and yellow-orange citrine zones within a single crystalline specimen. This striking color zoning is caused by variations in the oxidation state of iron trace elements during the crystal growth process, which is directly influenced by localized temperature and irradiation gradients across different crystal sectors. The distinct color combination typically forms in specific triangular patterns or bands inside the crystal structure. Because it requires highly specific geochemical and thermal fluctuations to develop naturally, nearly the entire global supply of natural commercial ametrine originates from the unique geological environment found at the Anahi deposit.

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