Original paper

Juangodoyite, Na2Cu(CO3)2, a new mineral from the Santa Rosa mine, Atacama desert, Chile

Schlüter, Jochen; Pohl, Dieter

Abstract

The new mineral juangodoyite has the ideal chemical formula Na2Cu(CO3)2. It is monoclinic with space group P21/a. Cell parameters refined from X-ray powder diffraction data are (Å) a = 6.171(4), β = 8.171(5), c = 5.645(4), b = 116.23(2)°, V = 255.33(15) Å3, Z = 2. Juangodoyite is isostructural with synthetic sodium bis(carbonato)cuprate(II). The strongest reflections in the X-ray powder diffraction data are as follows: [dmeas.(Å), I, (hkl)]: 2.666 (100, 11–2), 4.258 (75, 11–1), 5.056 (66, 001), 2.619 (65, 210) and 4.575 (57, 110). Juangodoyite was found at the Santa Rosa mine near Iquique, Atacama desert, northern Chile. It occurs as fine-grained pseudomorphs, with crystallites up to 5 μm in size, after small laths of chalconatronite (Na2Cu(CO3)2 · 3H2O). Its colour is a vivid ultramarine blue. The calculated density is 2.984g/cm3, the calculated average refractive index is 1.571. Juangodoyite is closely associated with chalconatronite, malachite, calcite, anhydrite and sodium hydrogen carbonates. Chemical analyses gave (wt.%) Na2O 28.27, CuO 33.77, CO2 38.45, sum 100.49. The resulting empirical formula calculated on the basis of 6 anions is Na2.08Cu0.98(C1.99O6).The mineral was named after Juan Godoy, discoverer of the Chañarcillo silver mine.

Keywords

juangodoyitenew mineralchalconatronitesodium bis(carbonato)cuprate(ii)chileatacamasanta rosa mine