This paper is based on observations made in the Cupp-Coutunn cave system of Turkmenistan. Genetic models for sulphate filamentary crystals in caves are often based on solutions seeping through porous substrates under some external hydrostatic pressure. The physical models of such seeping are examined and the seepage hypotheses found to be implausible for natural environments. The main genetic mechanism is shown to be only local feeding, exclusively due to capillary pressure together with a short-period (seasonal) humidity cycle. In some cases there is also a major role for sulphate reduction processes. Some new aggregates, based on filamentary crystal growth, are described.