New Minerals from the Redmond Mine, North Carolina, USA: IV. Haywoodite and Hanahanite, Two New Minerals Containing Gordaite-Like Sheets

Abstract

Abstract The new minerals haywoodite, [Pb(H2O)10)][Zn12(OH)20(H2O)(SO4)3] (IMA2021-115), and hanahanite, [Zn8(OH)14(SO4)]·3H2O (IMA2022-012), 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. Haywoodite has the following properties: colorless to pale pink pseudohexagonal tablets and barrel-like prisms up to about 0.5 mm in diameter; white streak; vitreous luster; brittle; Mohs hardness 2½; curved and stepped fracture; one perfect cleavage on {011}; 3.27(2) g/cm3 measured density; biaxial (−) with 1.588(2), β = 1.600(2), γ = 1.607(2), and 2V (meas.) = 76(2)°. Hanahanite has the following properties: light blue prisms up to 0.3 mm in length; white streak; vitreous luster; brittle; Mohs hardness 3; curved fracture; one very good cleavage on {001}; 3.28(2) g/cm3 measured density; uniaxial (−) with ω = 1.636(3) and ε = 1.620(3). Electron probe microanalyses provided the empirical formulae Pb1.36Zn11.97S3.00O43H41.33 and (Zn6.69Cu1.27Co0.01)Σ7.97S1.00O21H20.04 for haywoodite and hanahanite, respectively. Haywoodite is triclinic, P1¯, a = 8.35298(19), b = 13.2769(7), c = 18.2744(13) Å, α = 92.427(8), β = 90.419(6), γ = 108.214(4)°, V = 1922.94(18) Å3, and Z = 2. Hanahanite is hexagonal, P63, a = 8.312(2), c = 15.295(2) Å, V = 915.2(5) Å3, and Z = 2. The structures of haywoodite (R1 = 0.037 for 6876 I > 2σI) and hanahanite (R1 = 0.065 for 772 I > 2σI) both contain gordaite-like sheets. In the haywoodite structure, a disordered interlayer region contains approximately one Pb and ten H2O pfu. In the hanahanite structure, ZnO4 tetrahedra in adjacent sheets are linked by sharing corners and the interlayer region only contains an H2O group.