| It is imperative to try and develop a better understanding of the critical role of hydrogen in oxysalt minerals and the solutions they crystallize from; this will be accomplished using the experimental technique of single-crystal x-ray diffraction and the application of bond-valence theory. The main themes are (a) the arrangements of interstitial hydrogen bonds; (b) the effect of hydrogen on structure topology; and (c) how hydrogen, as a function of pH, affects speciation in aqueous solutions (specifically borate solutions) which in turn determines (in part) the minerals that crystallize from those solutions.;The effect of hydrogen on structure topology is examined in minerals of the MgSO4(H2O)n series, where n=0--7. These minerals are extremely sensitive to changes in the environment (presence of H2O, humidity); this is reflected in structural modifications to accommodate dehydration and rehydration.;The link between minerals and solutions is examined with respect to low-temperature hydrated borate minerals. It has been suggested that borate minerals crystallizing out of solutions utilize aqueous borate complexes to build their structural units, and that mineral structures may then be an indicator of the pH of the environment in which they form.;Interstitial hydrogen bonding is examined in the minerals with the general formula X2 M(TO 4)2(H2O)2, where X = Ca, Na; M = Mg, Fe2+, Mn2+, Co2+, Ni, Cu2+; T = P, As 5+, S6+. Minerals of X2 M(TO4)2(H2O) 2 general composition show three distinct structure-types with subtle yet significant differences in bond topology of the interstitial species. It is interstitial bonds that control the stability of minerals, as these weak bonds are more easily broken with changing conditions than the stronger bonds of the structural unit. |
