Gysinite, Pb(Nd,La)(CO3)2(OH) · H2O, a new lead, rare-earth carbonate from Shinkolobwe, Shaba, Zaire and its relationship to ancylite

Gysinite, ideally Pb(Nd,La)(CO₃)₂(OH)·H₂O, occurs at Shinkolobwe, Shaba, Zaïre, associated with schuilingite, malachite, cerussite, talc-chlorite, bornite, wulfenite, kasolite, native gold and garnet. The crystals, light pink to reddish pink in color, up to 1 mm in length, are euhedral with a pseudo-octahedral habit and with {111} and {110} as the most prominent forms. The streak is white to light pink. The name is to honor Professor Marcel Gysin. The crystal system is orthorhombic, space group Pmcn, with a = 5.04, b = 8.50, c = 7.25A and Z = 2. a: b: c ratio is 0.5929:1:0.8529. The calculated density is 4.82 g/cm³. X-ray diffraction data are similar to those of ancylite. The mineral is biaxial negative with 2V_x = 70°, 2V_calc = 72.4°, α = 1.745, β = 1.805, γ = 1.840, dispersion r < ν. Optical orientation: X = c, Y = a, Z = b.