Mysterious Origins Of Uruguay's World-Famous Amethyst Deposits Uncovered

PUBLISHED
22 hours ago

Researchers discovered these ancient amethyst geodes were formed at surprisingly low temperature

Rosie McCall
Freelance Writer

Edited
by
Johannes Van Zijl

Northern Uruguay is home to one of the largest amethyst deposits in the world – but their formation has long been a mystery. Using cutting-edge techniques, researchers are unraveling their origin story and have discovered that these stunning gems crystalized at surprisingly low temperatures.

Amethysts are a type of quartz, recognizable by their striking violet hue. The gemstones are an important economic resource in Uruguay, home to the Los Catalanes mining district–a deposit so significant it has been recognized as one of the “First 1000 IUGS Geological Heritage Sites” by the International Commission of Geoheritage (IUGS). According to the IUGS, the deposit is “unique” because of its high number of mega-geodes and vast reserves as well as the gemstone quality and variety.

Amethyst geodes (some over 16 feet high!) are located in cooled lava flows. These ancient lava flows can be traced to the breakup of the supercontinent Gondwana some 134 million years ago. Mining began in northern Uruguay over 150 years ago and continues to be an important industry today. However, because not much is known about their origin, it can be hard to find new geodes and much currently depends on miners’ experience.

To find out more, researchers carried out a series of geological surveys analyzing geode minerals, groundwater and geode-hosted water in over 30 mines. The study involved high-tech techniques including nucleation-assisted microthermometry (to examine small fluid-filled pockets in the rocks) and triple-oxygen-isotope geochemistry (to analyze oxygen atoms in minerals).

More:
https://www.iflscience.com/mysterious-origins-of-uruguays-world-famous-amethyst-deposits-uncovered-76436