New Minerals from the Redmond Mine, North Carolina, USA: V. Finescreekite and Hayelasdiite, Two New Thiosulfate Minerals Containing Cubane-Like Pb4O4 Structural Units

Abstract The new minerals finescreekite, Pb4 (OH) 4 (S2O3) 2 (IMA2022–030), and hayelasdiite, Pb4O1. 5 (OH) 2. 52Cu+5 (S2O3) 4 (S2O2OH) 2 (H2O) ·4H2O (IMA2022–021), were found in the Redmond mine, Haywood County, North Carolina, USA, where they occur in a highly unusual secondary assemblage that comprises a variety of rare Pb-Zn-Cu sulfates, thiosulfates, and carbonates. Finescreekite was found in close association with anglesite, cubothioplumbite, redmondite, and steverustite. Hayelasdiite was found in close association with anglesite and steverustite. Finescreekite properties: colorless tablets to about 1. 5 mm across; white streak; resinous to adamantine luster; brittle; Mohs hardness ∼ 2½; curved, stepped fracture; excellent cleavage on 001, fair on 100, 010, and 110; 5. 675 g/cm3 calculated density; biaxial (−) with α = 2. 00 (1), β = 2. 04 (calc), γ = 2. 065 (calc), 2V = 75. 9 (5) °. Hayelasdiite properties: colorless prisms and blades to about 0. 5 mm in length; white streak; vitreous to subadamantine luster; brittle; Mohs hardness ∼ 2½; curved fracture; perfect cleavage on 010; 4. 909 g/cm3 calculated density; biaxial (−) with α = 1. 89 (1), β = 1. 95 (calc), γ = 1. 97 (calc), 2V = 58 (5) °. Electron probe microanalyses provided the empirical formulae Pb4 (OH) 4 (S2O3) 1. 76 (SO4) 0. 24 and Pb4. 00O1. 5 (OH) 2. 52Cu+5. 00 (S2O3) 3. 24 (SO4) 0. 76 (S2O2OH) 2 (H2O) ·4H2O for finescreekite and hayelasdiite, respectively. Finescreekite is Orthorhombic, P212121, a = 8. 2330 (9), b = 10. 7128 (13), c = 14. 8256 (13) Å, V = 1307. 6 (2) Å3, and Z = 4. Hayelasdiite is triclinic, P, a = 7. 52089 (15), b =14. 9345 (3), c = 17. 9895 (13) Å, α = 106. 727 (8), β = 90. 966 (6), γ = 90. 031 (6) °, V = 1934. 79 (16) Å3, and Z = 2. The structures of finescreekite (R1 = 0. 061 for 1440 I 2σI) and hayelasdiite (R1 = 0. 055 for 5636 I 2σI) both contain cubane-like Pb4O4 clusters, Pb4 (OH) 44+ in finescreekite and Pb4O1. 5 (OH) 2. 52. 5+ in hayelasdiite. The structure of hayelasdiite also contains a decorated double chain with the formula Cu+5 (S2O3) 4 (S2O2OH) 2 (H2O) 5−.