Hydrous metal sulfate minerals associated with mine waste: Atomic structure, hydrogen bonding and phase equilibria.

摘要

The atomic structures and D-positions of deuterated goslarite, melanterite, bianchite, boyleite and ilesite have been refined in combined-histogram neutron-diffraction experiments. The results of the crystal-structure refinements are presented here and the H-bond network of each of these minerals is discussed in detail. H-bond networks have been compared between groups in an attempt to understand the hydration and dehydration behaviour of these minerals. Mineral equilibria at 23°C, with respect to relative humidity, were studied for a suite of metal-substituted specimens in a year-long hydration/dehydration experiment. The experiments were conducted in several glove-box relative-humidity chambers designed by the author. The results of these experiments are presented here and illustrate the different dehydration pathways that occur due to differences in chemical composition. Possible transitional or intermediate phases have been identified in the dehydration of melantente and epsomite. Minerals of the rozenite group have been observed during the dehydration of epsomite group minerals and hexahydrite group minerals were observed in the dehydration of melanterite group minerals. The possibility of intermediate phases in the non-equilibrium dehydration of minerals and the possibility of an unknown field of stability for these phases are presented. This study of H-bonding in metal sulfate minerals and mineral equilibria with respect to chemical composition and relative humidity is an important contribution to our understanding of the complex minerals associated with mine waste.