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 ...
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 ...
Crack open an unassuming stone, and you might just uncover a little conclave of crystals within. Their walls are glittering with quartz, amethyst, or calcite, protected by a hard shell that was shaped ...
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