Abstract
Sclarite, ideally (Zn,Mg,Mn)4Zn3(CO3)2(OH)10, is a new mineral species from the Franklin mine, New Jersey. It occurs as 1.5-mm clusters of clear, colorless crystals associated with leucophoenicite, gageite, zincite, and willemite. The mineral has a vitreous luster and white streak. It is brittle with no apparent cleavage and has a Mohs hardness of 3-4. Sclarite is biaxial positive with α = 1.648(1), β = 1.664(1), γ = 1.702(2), 2Vmeas = 63.4(6)°, 2Vcalc = 67°, with strong dispersion r ≫ v. It is monoclinic, space group A2/a, with a = 16.110(7), b =5.432(1), c = 15.041(10) Å, β = 95.490(4)°, and Z = 4. The strongest X-ray powder-diffraction lines are [d(Å), I, hkl] 7.50(10)(002), 3.75(4)(311,004), 3.63(5)(113,311), 3.53(4)(113,204), 3.398(2)(402), 2.934(2)(313), 2.621(5)(115), 2.500(4)(513,006). An electron-microprobe analysis gave FeO 0.1, MgO 6.7, MnO 4.2, ZnO 62.0, CO2 12.67 (calc.), H20 12.97 (calc.), total 98.6 wt%; Dobs = 3.51(5) and Dcalc = 3.547 g/cm3. The structure has been refined to R = 0.069. It is isostructural with loseyite, with Zn atoms occupying both the octahedral and tetrahedral sites. The mineral is named after Professor Charles B. Sclar of Lehigh University.