This project will investigate the genesis of repetitive, self- organization patterns of texture and composition in volcanic agates. These patterns are believed to be interlinked. Self- organization of a non-equilibrium system involves the spontaneous generation of a repetitive pattern without preexisting structures or periodic outside causes. The main patterns to be explored are (a) the systematic interlayering of bands made up of twisted chalcedony fibers with bands consisting of non-twisted fibers, (b) the associated oscillatory minor-element profile predicted by our present model and revealed by cathodoluminescence, and (c) the systematically fibrous, length-fast habit of agate quartz. The proposed research consists of quantitative dynamical modeling of agate crystallization by an autocatalytic mechanism, morphological instability analysis of the crystallization front, microscopic observations, and trace- and minor-element analyses by ion probe. These analyses will be carried out with the NSF-funded ion probe at MIT. This project will clarify the dynamics of a self- organizing system with geochemical, crystallochemical, and petrological significance, and geochemical factors controlling crystal morphology and crystalline textures.