Annealing of synthetic hammarite, Cu₂Pb₂Bi₄S₉, and the nature of cation-ordering processes in the bismuthinite-aikinite series

The progress of ordering of Cu⁺ and Pb²⁺ in synthetic hammarite, Cu₂Pb₂Bi₄S₉, has been monitored by the form and sharpness of satellite reflections in electron diffraction patterns and by high-resolution transmission electron microscopy (HRTEM). The results of annealing experiments indicate that in nature intermediate compositions in the bismuthinite-aikinite series consist of compositionally well-ordered polysome strips, which, depending on the initial composition and the cooling rate, may remain as disordered intergrowths (stacking disorder), form ordered intergrowths, or fully order into the supercell minerals. -from Author