title: The role and implications of bassanite as a stable precursor phase to gypsum precipitation.
abstract: Calcium sulfate minerals such as gypsum play important roles in natural and industrial processes, but their precipitation mechanisms remain largely unexplored. We used time-resolved sample quenching and high-resolution microscopy to demonstrate that gypsum forms via a three-stage process: (i) homogeneous precipitation of nanocrystalline hemihydrate bassanite below its predicted solubility, (ii) self-assembly of bassanite into elongated aggregates co-oriented along their c axis, and (iii) transformation into dihydrate gypsum. These findings indicate that a stable nanocrystalline precursor phase can form below its bulk solubility and that in the CaSO(4) system, the self-assembly of nanoparticles plays a crucial role. Understanding why bassanite forms prior to gypsum can lead to more efficient anti-scaling strategies for water desalination and may help to explain the persistence of CaSO(4) phases in regions of low water activity on Mars.
authors.affiliation: Laboratorio de Estudios Cristalográficos, Instituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Cientificas-Universidad de Granada, Av. de las Palmeras 4, 18100 Granada, Spain.
authors.forename: A E S
authors.initials: AE
authors.lastname: Van Driessche
authors.forename: L G
authors.initials: LG
authors.lastname: Benning
authors.forename: J D
authors.initials: JD
authors.lastname: Rodriguez-Blanco
authors.forename: M
authors.initials: M
authors.lastname: Ossorio
authors.forename: P
authors.initials: P
authors.lastname: Bots
authors.forename: J M
authors.initials: JM
authors.lastname: García-Ruiz