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JAGUEITE, Cu₂Pd₃Se₄, A NEW MINERAL SPECIES FROM EL CHIRE, LA RIOJA, ARGENTINA

Werner H. Paar^1,, Dan Topa¹, Emil Makovicky², Ricardo J. Sureda³, Milka K. de Brodtkorb⁴, Ernest H. Nickel⁵ and Hubert Putz⁶

¹ Department of Geography, Geology and Mineralogy, University of Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria
² Geological Institute, University of Copenhagen, Østervoldgade 10, DK-1350 Copenhagen K, Denmark
³ Cátedra de Mineralogía, Facultad de Ciencias Naturales, Universidad Nacional, 4400 Salta, Argentina
⁴ Consejo Nacional de Investigaciones Científicas y Técnicas, University of Buenos Aires, Paso 258-9A, 1640 Martinez, Argentina
⁵ Exploration and Mining, CSIRO, Private Bag no.5, PO Wembley, W.A. 1613, Australia
⁶ Department of Geography, Geology and Mineralogy, University of Salzburg, Hellbrunnerstr. 34, A-5020 Salzburg, Austria

E-mail address: werner.paar{at}sbg.ac.at

Jaguéite, with the simplified formula Cu₂Pd₃Se₄, the copper analogue of chrisstanleyite, was discovered in a telethermal selenide vein-type deposit at the El Chire prospect, Los Llantenes District of La Rioja Province, Argentina. The new mineral species is generally associated with chrisstanleyite, particularly in intimate intergrowths, clausthalite, naumannite, tiemannite, klockmannite, berzelianite, umangite and aguilarite. Mercurian silver, native gold, and two unnamed compounds, chemically (Ag,Cu)₆Hg₂Pd₂Se₃ and (Ag,Cu)₈Hg₃(S,Se)₇, occur as rare constituents. The selenide vein is hosted by metasedimentary rocks of Carboniferous age that belong to the Precordilleran terrane. Jaguéite occurs in anhedral grains that lack a distinct morphology. Aggregates of intergrown jaguéite and chrisstanleyite measure up to 100 x 20 µm; single grains, however, do not exceed 60 µm. The mineral is megascopically creamy yellowish in color, opaque and lacks internal reflections. It has a metallic luster and a black streak. It is brittle with an uneven fracture and without observable cleavage. VHN₂₅ ranges between 464 and 772 (mean 612) kg/mm², corresponding to a Mohs hardness of 5. In plane-polarized light, it is weakly to moderately bireflectant and slightly pleochroic, from light buff to creamy buff. Jaguéite is anisotropic; the rotation tints are brownish – bluish – greenish. The prominent spindle-shaped twins are almost identical to those in chrisstanleyite. The measured values of reflectance in air and oil, respectively, are 41.0–50.1, 27.0–31.9 (470 nm), 44.1–51.8, 29.2–33.8 (546 nm), 44.6–51.7, 29.4–33.7 (589 nm), 45.1–52.0, 30.2–34.1 (650 nm); values for 400–700 nm are tabulated. As an average, eight electron-microprobe analyses gave: Cu 15.7, Ag 1.59, Pd 42.04, Se 40.15, total 99.48 wt.%, corresponding to (Cu_1.91Ag_0.11)_2.02Pd_3.05Se_3.93 (basis: 9 atoms per formula unit). The ideal formula is Cu₂Pd₃Se₄, which requires Cu 16.68, Pd 41.88, Se 41.44, total 100.00 wt.%. Jaguéite has a monoclinic cell with a 5.672(5), b 9.910(9), c 6.264(6) Å, ß115.40(2)°, V 318.1(5)ų, space group P2₁/c and Z = 2. The calculated density is 8.01 g/cm³. The crystal structure was solved from single-crystal data obtained on a four-circle diffractometer with an area detector. The strongest eight lines in the calculated powder-diffraction pattern [d in Å(I)(hkl)] are: 2.759(23)(31), 2.676(100)(121), 2.630(64)(22), 2.508(31)(02), 2.269(27)(041), 1.950(27)(122), 1.920(36)(23) and 1.866(24)(41). Jaguéite and chrisstanleyite form a limited solid-solution series. The mineral is named after the village of Jagué, which is the closest settlement to the El Chire mine. Both the mineral and the mineral name were approved by the Commission on New Minerals and Mineral Names (IMA 2002–060).

Keywords: jaguéite, new mineral species, platinum-group mineral, Cu–Pd selenide, electron-microprobe data, reflectance data, X-ray-diffraction data, crystal structure, El Chire, Los Llantenes, La Rioja, Argentina.

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				D. Topa, E. Makovicky, and T. Balic-Zunic THE CRYSTAL STRUCTURES OF JAGUEITE, Cu2Pd3Se4, AND CHRISSTANLEYITE, Ag2Pd3Se4 Can Mineral, April 1, 2006; 44(2): 497 - 505. [Abstract] [Full Text] [PDF]