Discovered in 1999 inside an abandoned mine in Southern Spain, Pulpí Geode is the largest crystal 'cave' of its kind in the world. But what exactly is a geode and how do crystals form inside them?

And if you go to Put-in-Bay, you can tour the island's geode for yourself. Read more: 25 Gorgeous Islands For Vacationing ...

Geodes are hollow rock formations often with quartz crystals, such as amethyst, inside. Amethyst geodes in Uruguay have been found in cooled lava flows, which date from the original breakup of the ...

They can also appear on the Farm during the Winter, and inside Fishing Treasure Chests. You can take the geodes to Clint, who will break them open for 25g. Or, you can use a Geode Crusher to open ...