Helictites are contorted depositional speleothems which grow in any direction, seemingly defying gravity. They occur in many forms from tiny filaments (as in the top photo) to thick, antler-like forms (bottom photo). Most helictites are formed from calcite.
Helictites are formed by calcite-laden waters seeping through tiny pores in the rock. Hydrostatic pressure forces a small amount of the solution out, carbon dioxide is lost, and calcite is deposited. Growth continues through a tiny, central capillary chanel, which the solution flows through via hydrostatic and capillary pressure to emerge and deposit calcite at the tip.
Helictites are a very diverse group of speleothems, likely because different factors influence them. There is a very rare category that forms underwater, best known from Lechuguilla Cave, New Mexico. One show cave in California, Black Chasm Cavern, was designated a National Natural Landmark because of this. Visit our special tribute page to this cave’s diverse helictites.
The twisted shapes are due to many factors, including:
(1) impurities in the deposited calcite
(2) wedge-shaped crystals causing uneven deposition
(3) plugging of the central channel may occur in dry periods, and when flow resumes, the pressure may force a new channel out the side of the original one
(4) air currents may favor growth in a particular direction. Sometimes helictites are found facing the same direction down a passage (see upper left photo in thumbnail table below).
AUTHOR: Dave Bunnell