The Ochtinská Aragonite Cave, in southern Slovakia, is one of the few caves in the world where aragonite crystals are found. There is one in the Czech Republic (Zbrašov aragonite caves) and other caves are located in Brazil, Argentina, Mexico and the United States, but the aragonite fillings in Ochtinská Aragonite Cave is by far the most beautiful.
Aragonite is a naturally occurring crystal form of calcium carbonate, the same mineral that forms the more commonly available calcite. While calcite forms huge lumpy blocks, aragonite crystals are columnar or fibrous. In Ochtinská Aragonite Cave, they grow in twisted, needle like formations that look like a bunch of tangled hair. These structures are very delicate and can break at the slightest touch. Crystal structures such as these are known as helictites, and to this day, there has been no satisfactory explanation for how they are formed.
Photo credit: Traveltipy/Flickr
A helictite starts out as a tiny stalactite — those icicle-shaped formation that hangs from the ceiling of a cave. They are formed by the precipitation of minerals —calcium carbonate, in this case— dissolved in water that drip down through the porous rocks of the cave ceiling. But instead of growing vertically down, the stalactite starts to wander, twisting and turning as it grows. Sometimes the stalactite will grow normally but a number of secondary root like growths will pop out from the sides.
What causes the stalactite to break form is still a mystery, although there are a few theories. Capillary forces might be responsible for drawing water along paths against gravity. Or the wind might blow the stalactites to different directions. But these theories are problematic. The majority of helictites are not hollow, so capillary forces can’t act, and many caves have no entrance where wind could enter.
The Ochtinská Aragonite Cave was discovered accidentally in 1954. While looking for iron ore, explorers dug through the ground and stumbled upon the cave. Prior to its discovery, the cave had no natural entrances. Since it opened to the public in 1972, nearly 30,000 people has been visiting the cave each year to appreciate the rare beauty of its crystals. The most impressive is Milky Way Hall which is covered with white bunches of aragonite, glowing in the lamplight like stars in the night sky. Some of the oldest aragonite crystals at Ochtinská are 138,000 years old.
Photo credit: Jean-Marie Prival/Flickr
Photo credit: Jean-Marie Prival/Flickr
Photo credit: Peter Fenda/Flickr
Photo credit: Erwin/Flickr
Photo credit: Traveltipy/Flickr
Photo credit: Jean-Marie Prival/Flickr
Sources: www.slovakia.com / www.go2slovakia.eu / Wondermondo / Wikipedia
Re: aragonite. Should have given some ida of scale for reference. Hard to tell what size of crystals is.
ReplyDeleteAs a rough guess the bottom photo shows an area about 30 cm wide. The rounded tips you can see on some of the needles are probably about the size of a drop of water. These examples are pretty enough, but look very similar to helictites that are formed from calcite (which commonly appears in far better forms than "lumpy blocks").
ReplyDeleteAragonite is much more common than the article suggests, and is found in far more than just a "few caves". One of the distinguishing characteristics of most aragonite is that it tends to form very spiky formations that are far different than most calcite formations, and there are much better examples than what's presented here. A Google image search for lechuguilla aragonite will turn up some very nice examples.