Imagine a cave where the walls are covered with huge, sparkling crystals, some as big as trees. This isn’t a scene from a ...

Archaeologists investigating caves in Malaysia ahead ... they commonly included stone tools; hematite minerals, or red ochre; ...

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?