High-angle annular dark field scanning transmission electron microscopy (HAADF STEM) is a powerful Z-contrast technique able to depict the structural motifs in Pb-(Bi-Sb)-sulfosalts. Using two homologues from the kobellite homologous series, a group of “chessboard derivative structures” represented by Bi- and Sb-rich pairs of natural phases, we visualise the units which underpin the complex crystal structure modularity in these minerals.
High resolution STEM imaging reveals nano-scale intergrowths and replacement throughout the mineral, which are used to explain compositional variation of this mineral at the micron-scale.