Zoharite

The Fe analogue of owensite. Also Ba analogue of gmalimite.


The primary structural units of these minerals are M8S14 clusters, composed of MS4 tetrahedra surrounding a central MS6 octahedron. The M site is occupied by transition metals such as Fe, Cu, and Ni. These clusters are further connected via the edges of the MS4 tetrahedra, forming a close-packed cubic framework. The channels within this framework are filled by anion-centered polyhedra: SBa9 in zoharite and SK9 in gmalimite, respectively. In the M8S14 clusters, the M atoms are positioned so closely that their d orbitals can overlap, allowing the formation of metal–metal bonds. As a result, the transition metals in these clusters often adopt electron configurations that reflect additional electron density from their local bonding environment, similar to what is observed in pentlandite. Due to the presence of shared electrons in these metal–metal bonds, assigning fixed oxidation states—such as Fe2+/Fe3+ or Cu+/Cu2+—becomes challenging. Moreover, modeling the distribution of mixed-valence cations (Fe2+/3+, Cu+/2+, and Ni2+) across the two distinct M sites—one located in the MS6 octahedron and the other in the MS4 tetrahedra—often results in ambiguous outcomes. Consequently, it is difficult to define an idealized end-member formula for these minerals.