Helictite

thumb|Rare "fishtail" helictites in the Caverns of Sonora near [[Sonora, Texas]] thumb|A helictite at Treak Cliff Cavern in [[Derbyshire]]

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. Helictites 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.