Crystal chemistry of the natrojarosite-jarosite and natrojarosite-hydronium jarosite solid-solution series: A synthetic study with full Fe site occupancy

Abstract

Members of the natrojarosite-hydronium jarosite [(Na,H 3 O)Fe 3 (SO 4 ) 2 (OH) 6 ] and jarosite-natrojarosite [(K,Na)Fe 3 (SO 4 ) 2 (OH) 6 ] solid-solution series were synthesized and investigated by Rietveld analysis of X-ray powder diffraction data. The synthesized samples have full Fe occupancy, where in many previous studies there were significant vacancies in the B site. Well-defined trends can be seen in the unit-cell parameters across the solid-solution series in the synthetic samples. The majority of the samples in this study were directly synthesized under hydrothermal conditions at 140 °C. End-member natrojarosite was synthesized using a two-step method, where the initial sample was heated in a 1.0 m H 2 SO 4 -0.5Na 2 SO 4 solution at 200 °C for 3 days, yielding a sample with 100% Na occupancy. Many of the samples were initially zoned and required grinding and re-heating in the reactant solution for homogenization. Substitution of H 3 O and K into natrojarosite changes unit-cell parameters in a linear fashion. The unit-cell parameters presented here are significantly different than the majority of previous studies on synthetic samples, as samples in the current study have full Fe occupancy and the Na-K jarosite series has no H 3 O substitution in the A site. Substitution in the A site mainly affects unit-cell parameter c with little change in a. As Na occupancy increases there is a decrease in A-O2 and A-O3 distances and a consequent increase in Fe-O2 and Fe-O3 distance leading to an overall decrease in unit-cell parameter c in both the Na-H 3 O and Na-K jarosite series. The synthetic samples are compared to natural samples from mine waste deposits in Rio Tinto (Huelva, Spain), Ely Mine (Vermont), and a mineral collecting locality near Sharbot Lake (Ontario), as well as natural and synthetic samples documented in the literature. Based on unit-cell parameters many of the natural samples appear to have full Fe occupancy and correlate well with the synthetic samples from this study. The infrared spectra of the samples were analyzed, and there is a gradual change in the spectral features across the solid-solution series between end-members. The results from this study will aid in the interpretation of the possible chemical compositions of natural jarosite group minerals in mine waste and on Mars.

Single-crystal X-ray diffraction study of synthetic sodium–hydronium jarosite

“…Our unit cell data fall close to the linear a-c trend refined from powder data of Na-H 3 O jarosite solid solutions (Fig. 3 in Basciano and Peterson 2008).…”

“…The sealed reaction vessel was placed inside a furnace and heated at 413 K for 8 days. The synthesis time was four times longer than described in Basciano and Peterson (2008) to promote the growth of large crystals.…”

“…Na-H 3 O jarosite was synthesised using a similar method as described by Basciano and Peterson (2008). A 75-ml Parr pressure vessel was used as the reaction chamber.…”

Crystallization of Jarosite with Variable Al3+ Content: The Transition to Alunite

“…Therefore, the lack of natural intermediates more likely reflects formation conditions. The work of Basciano and Peterson [24] mentions that, in many samples, vacancies can exist in both the A position (where the monovalent cation is found) and the octahedral B position (occupied by the Al or Fe ion in this case). Vacancies can result in hydronium ion substitution elsewhere in the structure for charge balancing reasons.…”

Investigation of thermal decomposition of jarosite tailing waste

“…Nowadays, jarosite has been in the headlines of many researchers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] aiming at its use in sulfoaluminate cement production [2], ordinary Portland cement production [7], brick production [5] or silver recovery [8]. Jarosite structure can accommodate many other elements [10][11][12][13][14]. The waste released from hydrometallurgical process besides jarosite contains amorphous as well, whereas enlarged amorphous presence can make the crystalline identification more difficult.…”