Fibrous morphologies were obtained from two tetrasubstituted adamantanes. One fiber consisted of crystals having aspect ratios of 2-3 orders of magnitude. According to X-ray analysis, the crystals are endowed with a series of weak hydrogen bonds which, through cooperative action born of a precise surface-to-surface fit, leads to a preferred one-dimensional growth. The second adamantane derivative(a tetracation) forms flexible fibers up to 2 cm long when grown by the solvent diffusion method. Scanning electron microscopy shows a "rhythmic" morphology in which the fibers are composed of thin submicron plates, with rectangular or hexagonal geometries, stacked one upon another. Because the plates are congruent, the terminal plate of a growing fiber must act as a template that controls the dimensions of a plate that is in the process of forming contiguously. This unprecedented form of matter is explained on the basis of Liesegang ring theory. Anecdotal evidence supporting a Liesegang mechanism comes from yet another adamantane compound that crystallizes from solution in the form of horizontal rings. Interest in Liesegang phenomena stems in part from their possible relationship to natural periodicity as found, for example, in banded agates and gallstones.