Slovakia: Ochtinska Aragonite Cave (Slovak Karst NP)
Ochtinska Aragonite Cave is drastically different from any other caves with formations one would expect to see – the formations here are those of aragonite crystals, a rather rare amorphous form of calcium carbonate. Unlike traditional stalactites and stalagmites that form from calcite deposited from the running or dripping water, aragonite crystals grow in all possible directions in the damp environment of the cave, forming beautiful otherworldly cave flowers on the walls and ceilings. Pure crystal aragonite is very rare and there are only three pure aragonite caves in the world. Ochtinská Aragonite Cave is famous for its Milky Way Hall where aragonite flowers cover the entire ceiling and shine like the stars. “Aragonite’s crystal lattice differs from that of calcite, resulting in a different crystal shape, an orthorhombic system with acicular crystals. Repeated twinning results in pseudo-hexagonal forms. Aragonite may be columnar or fibrous, occasionally in branching stalactitic forms called flos-ferri (“flowers of iron”) from their association with the ores at the Carinthian iron mines” (from Wiki). Naturally, it’s protected as UNESCO World Heritage Site.