Imagine walking through a dusty, arid landscape when you stumble upon a seemingly ordinary rock. Its rough exterior might not catch the eye, but what lies within surely will. Geodes are one of ...

Amethyst is a violet variety of quartz that has been used as a gemstone for many centuries and is a key economic resource in northern Uruguay. Geodes are hollow rock formations often with quartz ...

Amethyst geodes—some stretching 5 m long—dot the ancient lava flows of Uruguay’s Los Catalanes mining area. The geodes contain calcite, colorless quartz, and agate, another quartz mineral. Large ...

Göttingen University researcher Fiorella Arduin Rode working in open pit mine of the study area, Los Catalanes mining district, northern Uruguay. Along with Ametista do Sul in southern Brazil, these ...

Gabriela Farfan, the Smithsonian's curator of gems and minerals, answers the internet's burning questions about gemstones. Are all minerals crystals? How are diamonds cut? How do geodes form? Is the ...