Erazoite, a new copper tin sulfide from the El Guanaco gold deposit, Antofagasta Province, Chile
Schlüter, Jochen; Malcherek, Thomas; Stanley, Chris; Dini, Maurizio; Donoso, Arturo Molina
published: Jan 1, 2017
The mineral erazoite (IMA 2014-061) is a new copper tin sulfide structurally related to covellite. Erazoite is rhombohedral with space group R 3m. Cell data refined from powder diffraction data are a = 3.756(8), c = 32.91(4) Å, V = 402.1(2) Å3 and Z = 2. The strongest X-ray powder reflections are as follows, d obs. (Å) (I; hkl): 3.022 (100; 104), 1.877 (47; 110), 1.667 (13; 119) and 1.592 (12; 024). Chemical analyses gave (wt.%): Cu 42.46, Sn 20.99, Fe 0.01, In 0.26, S 34.42, sum 98.14 wt.%. The resulting empirical formula based on 6 S pfu is Cu3.74 Sn0.99 In0.01 S6. The simplified formula is Cu4 SnS6, which requires Cu 44.96, Sn 20.99, S 34.04, total 99.99 wt.%. The new mineral was found in 2012 in the Chilena mine at the El Guanaco ore deposit, Northern Chile. Erazoite occurs as tiny black roundish crystal aggregates enclosed in baryte crystals. Its colour in reflected plane polarized light is grey with reflectance values of 19.7 to 27.2 (Ro, Re' at 589 nm) and distinct pleochroism, which appears pinkish to grey against fahlore. Erazoite additionally has a strong anisotropy with characteristic orange-buff to deep red-brown to muddy green colours.