Comparative modular analysis of two complex sulfosalt structures: sterryite, Cu(Ag,Cu)₃Pb₁₉(Sb,As)₂₂(As–As)S₅₆, and parasterryite, Ag₄Pb₂₀(Sb,As)₂₄S₅₈

The crystal structures of two complex minerals of the lead sulfosalt type, sterryite, Cu(Ag,Cu)₃Pb₁₉(Sb,As)₂₂(As–As)S₅₆, and parasterryite, Ag₄Pb₂₀(Sb,As)₂₄S₅₈, were solved and compared according to modular analysis. These quasi-homeotypic structures are expanded derivatives of owyheeite, Ag₃Pb₁₀Sb₁₁S₂₈.