Synthetic minerals analyses. The process of bulk precipitation for mineral formation is estimated to be analogous to the one that occurs in hydrothermal vent system resulting in its typical porous inorganic barriers that form the vent mounts. The XRD analyses of those minerals showed the typical profile from amorphous or nanocrystaline structures (see Supplementary material), likely due to the formation of several phases simultaneously. XRF (Fig. ) suggests similar stoichiometric ratios of metal (Fe or Fe/Ni) to S present in the precipitated minerals.