Chemical vapor transport growth and crystal structure of Pb-Sb sulfosalts

Zinkenite (ideally Pb₉Sb₂₂S₄₂) and Boulangerite (ideally Pb₅Sb₄S₁₁) are two Naturally occurring minerals that are predominantly ternary compounds of Pb-Sb-S with some impurities.  We recently synthesized single crystals of these materials in the laboratory by chemical vapor transport (CVT) in a vacuum-sealed quartz tube. Both samples were grown in an acicular shape where the zinkenite needles formed a textile shape similar to wool. Single crystal X-ray diffraction measurement have been performed to explore the crystal structure at room temperature.  The Rietveld refinement of single-crystal XRD data has been performed that confirms that the Zinkenite crystallizes within hexagonal symmetry with lattice parameters a = 22.0965(4) Å and c = 4.31990(10) Å whereas the Boulangerite sample crystallizes within monoclinic symmetry with lattice parameters a = 8.04786(13) Å, b = 23.4732(4) Å, c = 21.5621(5) Å, and β = 100.7410(19) degrees. Further, the energy-dispersive X-ray spectroscopy (EDS) shows that the stoichiometry of Zinkenite sample is roughly Pb₁₂Sb₃₂S₅₄. Physical properties of these samples will be reported.