Helictite

A helictite is a speleothem (cave-formed mineral) found in a limestone cave that changes its axis from the vertical at one or more stages during its growth.

But the dripstones grow very slowly – several centimeters in 100 years – meaning that the wind direction would have to stay steady for long periods of time, changing for every fragment of a millimeter of growth.

Another hypothesis that has been proposed is that slowly changing geological pressure causing stresses on the crystals at the base alters the piezo electrostatic potential and causes particle deposition to be oriented in some relationship to the prevailing pressure orientation.

A recent hypothesis, which is supported by observation, is that a prokaryotic bacterial film provides a nucleation site for mineralization process.

The direction of the end of the straw may wander, twist like a corkscrew, or the main part may form normally while small helictites pop out of its side like rootlets or fishhooks.

When helictites are found on cave floors, they are referred to as heligmites, though there is debate as to whether this is a genuine subcategory.

For an unknown reason, when the chemical composition of the water is slightly altered, the single crystal structure can change from a cylindrical shape to a conical one.