Abstract

Huenite, Cu4Mo3O12(OH)2, is a new copper and molybdenum oxy-hydroxide mineral found in the San Samuel Mine, Carrera Pinto, Cachiyuyo de Llampos district, Copiapó Province, Atacama Region, Chile. This new species forms flattened orthorhombic prisms up to 60–70 μm in size, weakly elongated along [001]. Huenite crystals were found on fractured surfaces of a quartz breccia, forming aggregates 1 mm in diameter in close association with lindgrenite, gypsum, dark grayish-brown tourmaline, and an unknown pale purple phase. The color is very dark reddish-brown, with a strong vitreous to adamantine luster. Its streak is pale reddish-brown to pinkish. The mineral is brittle with an irregular fracture and a Mohs hardness of 3.5–4 with a good cleavage on {010}. Its calculated density is 5.1 g/cm3. The calculated refractive index is 2.18. Huenite is non-fluorescent under 254 nm (short wave) and 366 nm (long wave) ultraviolet light. The empirical formula, calculated on the basis of 3 (Mo+S+Si) atoms per formula unit, is (Cu3.519Fe2+0.403)Σ3.922(Mo2.907S0.090Si0.003)Σ3.000O12·(OH)2.229, with H2O content calculated for a total of 100 wt.%. Huenite is trigonal, with space group P31/c and unit-cell parameters a = 7.653(5) Å, c = 9.411(6) Å, and V = 477.4(5) Å3 for Z = 2. The eight strongest measured powder X-ray diffraction lines are: [d in Å, (I/I0), (hkl)]: 2.974 (100) (112), 1.712 (59.8) (132), 3.810 (50.6) (110), 2.702 (41.2) (022), 2.497 (38.1) (120), 1.450 (37.2) (134), 6.786 (24.9) (010), and 5.374 (24.5) (011). The mineral, which has been approved by the CNMNC under number IMA 2015-122, is named in honor of Edgar Huen.

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