Geodes are hollow rock filled with dazzling crystals. I'm at the American Museum of Natural History in New York City and behind me is an amethyst geode that was formed millions of years ago. Geodes ...
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 ...
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