Reintroducing sborgite: Crystallization through exposure of sodium borosilicate glasses to moisture

•Mono-crystalline phase sborgite, for the very first time, was prepared in laboratory instead of being found in geological depository.•A novel moisturizing vacuum desiccator setup was used to conduct the experiment.•All prepared glasses after moisturizing has been confirmed containing sborgite mono-crystalline phase.•First SEM image of sborgite crystals was presented.

Sborgite (Na[B5O6(OH)4]·3H2O) is a rare mineral, naturally occurring in only 2 known locations worldwide: California, USA and Larderello, Italy. Little is known of this mineral given its rarity in the natural world as well the inability, until now, to be produced in a single crystalline product. For the first time, we reported a single crystalline sborgite crystallization phenomenon caused by exposure of two different sodium borosilicate glasses to moisture. In this study, two homogeneous and two phase separated borosilicate glasses were prepared and exposed to moisture at room temperature (~25 °C) for up to 1 month. The powders were characterized by X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM). The results showed that exposure of all sodium borosilicate glasses to moisture can lead to crystallization of sborgite micro-crystals with a column-like morphology. In addition, it is shown that exposure of homogeneous glasses to humidity results in the formation of more highly crystalline sborgite than phase separated glasses of equal composition.

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