Ultimately, the researchers narrowed down the geode's formation to a window of about 2 million years (not bad for the 4.5-billion-year-old calendar of geologic time).

Researchers have revealed the geological processes behind the formation of amethyst and agate geodes in Northern Uruguay’s Los Catalanes District, offering new insights into mineral composition ...

Amethyst geodes in Uruguay have been found in cooled lava flows, which date from the original breakup of the supercontinent Gondwana around 134 million years ago. However, their formation has ...

Mystery of Uruguay's amethyst geodes: New model to explain amethyst formation. ScienceDaily . Retrieved June 2, 2025 from www.sciencedaily.com / releases / 2024 / 10 / 241002135231.htm ...