Helictite

A helictite is a speleothem found in limestone caves that changes its axis from the vertical at one or more stages during its growth. They have a curving or angular form that looks as if they were grown in zero gravity. They are most likely the result of capillary forces acting on tiny water droplets, a force often strong enough at this scale to defy gravity. They are formed by biologically-mediated processes, rather than abiotic processes as scientists previoulsy thought.

Helictites are, perhaps, the most delicate of cave formations. They are usually made of needle-form calcite and aragonite. Forms of helictites have been described in several types: ribbon helictites, saws, rods, butterflies, "hands", curly-fries, and "clumps of worms." They typically have radial symmetry. They can be easily crushed or broken by the slightest touch. Because of this, helictites are rarely seen within arm's reach in tourist caves.

Timpanogos Cave National Monument in Utah has one of the largest collections of these formations in the world. The large numbers are also in the Jenolan Caves in Australia and in the Pozalagua Cave in Karrantza in Spain. A remarkable suite of helictites is also occurring in Asperge Cave in France.

The growth of helictites is still quite enigmatic. To this day there has been no satisfactory explanation for how they are formed. Currently, formation by capillary forces is the most likely theory, but another theory based on wind formation is also viable.

The most likely theory explains helictites as a result of capillary forces. If the helictite has a very thin central tube where the water flows like it does in straws, capillary forces would be able to transport water against gravity. This theory was inspired by some hollow helictites. However, the majority of helictites are definitely not hollow. Despite this, droplets can be drawn to the tips of existing structures and deposit their calcite load almost anywhere thereon. This can lead to the wandering and curling structures seen in many helictites.

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Wikipedia