Sanromanite, Na2CaPb3(CO3)5, from the Santa Rosa mine, Atacama desert, Chile, a new mineral of the burbankite group
Schlüter, Jochen; Malcherek, Thomas; Pohl, Dieter
published: Feb 28, 2007
ArtNo. ESP154018302001, Price: 29.00 €
The new mineral sanrománite (IMA-CNMMN No. 2006-009) has the ideal chemical formula Na2CaPb3(CO3)5. It is hexagonal with space group P63mc. Unit cell data from single-crystal X-ray studies gave (Å) a = 10.570(1), c = 6.651 (1), V = 643.5(2) Å3, Z =2. Cell parameters refined from X-ray powder diffraction data are (Å) a = 10.553(1), c = 6.641(1), V = 640.5(2) Å3. Sanrománite is the Pb-dominant analogue of burbankite, calcioburbankite and khanneshite. The strongest reflections in the X-ray powder diffraction data are as follows: (dmeas.(Å), I, (hkl)): 3.769 (100, 20.1), 2.640 (65, 22.0), 3.066 (51, 21.1), 2.688 (50, 20.2), and 2.161 (50, 40.1). Sanrománite was found at the Santa Rosa mine near Iquique, Atacama desert, northern Chile. It occurs as radiating acicular or artichoke-like aggregates and as isolated needles. Fine needles appear colorless, aggregates show a greenish-yellow color. The calculated density is 5.20 g/cm3. The mineral is optical negative with a calculated average refractive index of 1.822. Sanrománite is closely associated with malachite, calcite, anhydrite, chalconatronite, sodium-hydrogen carbonates and the recently described new mineral juangodoyite. Chemical analyses gave (wt.%) Na2O 6.04, CaO 5.64, PbO 65.86, CO2(norm.) 21.84, sum 99.38. The resulting empirical formula based on 15 anions is Na1.97Ca1.02Pb2.98C5.01O15. The name is for the Chilean naturalist (mineralogy and geology) Francisco J. San Román (1834-1902).