Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original paper

Jiří Sejkora, Cristian Biagioni, Zdeněk Dolníček, Panagiotis Voudouris

Arsenogoldfieldite, Cu₁₂(As₂Te₂)_Σ4S₁₃, a new tetrahedrite-group mineral

Journal of Geosciences, volume 70 (2025), issue 1, 33 - 42

DOI: http://doi.org/10.3190/jgeosci.0034.25

Arsenogoldfieldite is a new mineral discovered in a sample collected from the North Star mine, Mammoth, Tintic district, Juab County, Utah, U.S.A (type locality). It occurs as anhedral grains, up to 300 μm in size, in a quartz gangue, associated with tellurium, enargite including Sn-bearing variety and supergene juabite. Arsenogoldfieldite is black, with a metallic luster. Mohs hardness is ca. 3½-4; calculated density is 4.954 g.cm^-3. In reflected light, arsenogoldfieldite is grey with a brownish shade; it is isotropic. Internal reflections were not observed. Reflectance values for the four COM wavelengths in air [R (%) λ (nm)] are: 30.2(470); 29.9(546); 29.9 (589); and 30.4 (650). The empirical formula of arsenogoldfieldite is Cu_11.75Zn_0.03Fe_0.02[(As_1.44Sb_0.43Bi_0.13)_Σ2.00Te_2.00]S_13.11. The ideal formula is Cu₁₂(As₂Te₂)S₁₃, which requires (in wt. %) Cu 48.13, As 9.46, Te 16.11, S 26.30, total of 100.00. Arsenogoldfieldite is cubic, I-43m, with unit-cell parameters a = 10.2868(4) Å, V = 1088.53(13) ų, Z = 2. The strongest reflections of the X-ray powder diffraction pattern [d, Å (I) hkl] are: 3.638 (8) 220, 2.969 (100) 222, 2.573 (9) 400, 1.8187(21) 440 and 1.5504(9) 622, According to the single-crystal X-ray diffraction data (R = 0.0221 on the basis of 380 unique reflections with F_o > 4σF_o and 22 refined parameters), arsenogoldfieldite is isotypic with other tetrahedrite-group minerals. Arsenogoldfieldite is named in agreement with the nomenclature of the tetrahedrite group as the (As/Te) end-member in the goldfieldite series. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (2022-084). The description of arsenogoldfieldite from the Pefka mine, Alexandroupoli, Western Thrace, Greece (cotype locality), its chemical composition and crystal structure data are also given in the paper.