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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.
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.
== Formation ==
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.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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