Adanite, a new lead-tellurite-sulfate mineral from the North Star mine, Tintic, Utah, and Tombstone, Arizona, USA

Adanite, Pb₂ (Te⁴⁺O₃)(SO₄), is a new oxidation-zone mineral from the North Star mine, Tintic district, Juab County, Utah, and from Tombstone, Cochise County, Arizona, USA. The characterization of the species is based principally on North-Star holotype material. Crystals are beige wedge-shaped blades, up to about 1 mm in length, in cockscomb intergrowths. The mineral is transparent with adamantine luster, white streak, Mohs hardness 2½, brittle tenacity, conchoidal fracture, and no cleavage. The calculated density is 6.385 g/cm³. Adanite is biaxial (–), with α = 1.90(1), β = 2.04(calc), γ = 2.08(calc), 2V(meas) = 54(1)°. The Raman spectrum is consistent with the presence of tellurite and sulfate groups and the absence of OH and H₂O. Electron-microprobe analyses gave the empirical formula Pb_(1.89)Sb³⁺_(0.02)Te⁴⁺_(0.98)S⁶⁺_(1.04)Cl_(0.02)O_(6.98). The mineral is monoclinic, space group P2₁/n, with a = 7.3830(3), b = 10.7545(5), c = 9.3517(7) A, β = 111.500(8)°, V = 690.86(7) A₃, and Z = 4. The four strongest X-ray powder diffraction lines are [dobs A(I)(hkl)]: 6.744(47)⁠, 3.454(80)⁠, 3.301(100)⁠, and 3.048(73)⁠. The structure (R₁ = 0.022 for 1906 I > 2σI reflections) contains Te⁴⁺O₃ pyramids that are joined by short (strong) Pb–O bonds to form sheets. Interlayer SO₄ groups link the sheets via long Pb–O and Te–O bonds.