JUABITE, CU-5(TE6-DOT-3H(2)O, A NEW MINERAL SPECIES FROM THE CENTENNIAL EUREKA-MINE, JUAB COUNTY, UTAH(O4)(2)(AS5+O4)(2)CENTER)

Juabite, ideally Cu-5(Te6+O4)(2)(As5+O4)(2) . 3H(2)O, is triclinic, sp ace-group choices P1(1) <P(1)over bar (2)>, with unit-cell parameters refined from powder data: a = 8.984(5), b = 10.079(7), c = 8.975(5) An gstrom, alpha = 102.68(7)degrees, beta = 92.35(6)degrees, gamma = 70.4 5(5)degrees, V = 746.8(8) Angstrom(3), a:b:c = 0.8914:1:0.8905, Z = 2. The strongest seven reflections of the X-ray powder-diffraction patte rn [d in Angstrom (I)(hkl)] are: 9.28 (70)(010), 4.65 (70)(020), 3.097 (100)(030,<(2)over bar 11>), 3.018 (60)(212), 2.658 (50)(<(3)over bar 01>), 2.368 (50)(<(2)over bar 2>(2) over bar) and 1.740 (50)(<(1)over bar 1>(5) over bar, 521, <(1)over bar 5>(1) over bar). The mineral is an extremely rare constituent on the dumps of the Centennial Eureka m ine, Juab County, Utah, U.S.A., where it occurs as crystalline platy m asses that average 0.2-0.3 mm in longest dimension within small interc onnected vugs of drusy quartz. Associated minerals are enargite, beuda ntite, and an undefined, possible Pb-analogue of arsenobismite. indivi dual crystals are subhedral to euhedral and average 125 x 100 x 1-2 mu m in size. Cleavage {010} perfect. Forms are: {010} major; (100), {<( 1)over bar 01>}, and {101} minor. The mineral is translucent (masses) to transparent (crystals), emerald-green, with a pale green streak, an d an uneven to subconchoidal fracture. Juabite is vitreous to adamanti ne (almost gemmy) on cleavage faces, brittle, and nonfluorescent; H (M ohs) 3-4; D (calc.) 4.59 g/cm(3) for the idealised formula. In polishe d section, juabite is white in plane-polarised reflected light in air with ubiquitous turquoise-blue internal reflections; bireflectance and anisotropy are unknown (due to interference from internal reflections ). Averaged electron-microprobe analyses yielded CuO 38.25, PbO 0.57, TeO3 32.58, As2O5 22.81, H2O (calc. assuming 3H(2)O) [5.19], total [99 .40] wt.%, leading to the empirical formula (Cu5.01Pb0.03)(Sigma 5.04) (TeO4)(1.93)(AsO4)(2.07). 3.00H(2)O based on O = 19. The infrared abso rption spectrum shows definite bands for structural H2O with an O-H st retching frequency centred at 3283 cm(-1) and a H-O-H flexing frequenc y centred at 1642 cm(-1). The mineral name is for the county within th e state of Utah in which the Centennial Eureka mine is located.