FRANKHAWTHORNEITE, CU2TE6-EUREKA MINE, TINTIC DISTRICT, JUAB COUNTY, UTAH(O4(OH)(2), A NEW MINERAL SPECIES FROM THE CENTENNIAL)

Frankhawthorneite, ideally Cu2Te6+O4(OH)(2), is monoclinic, P2(1)/n (1 4), with unit-cell parameters refined from powder data: a 9.095(3), b 5.206(2), c 4.604(1) Angstrom, beta 98.69(2)degrees V 215.5(1) Angstro m(3), a:b:c 1.7470:1:0.8844, Z = 2. The strongest eight lines of the X -ray powder-diffraction pattern [d in Angstrom(l)(hkl)] are: 4.505(40) (110, 200), 4.337(60)((1) over bar 01), 3.838(50)(101), 2.891(70)((2) over bar 11), 2.598(100)(020,310,211), 1.834(40)((3) over bar 12), 1.7 13(40)(022) and 1.500(40)(330,231,600). The mineral is found on the du mps of the Centennial Eureka mine, Juab County, Utah, where it occurs as isolated crystals 0.1 mm in size or as groupings of crystals on dru sy white quartz. Associated minerals include mcalpineite, pyrite, hema tite, acanthite, chrysocolla, connellite, enargite, hinsdalite, svanbe rgite and an undefined Cu-Zn-Te-bearing pale green botryoidal crust. I ndividual crystals of frankhawthomeite are prismatic to stubby bladed, are subhedral to euhedral, and have slightly curved faces. They are e longate [001], with a length-to-width ratio of approximately 3:1. Form s are {010} major, and possible {100} and {011} minor. The mineral is transparent, medium leaf green, with a less intense streak of the same color and an uneven fracture. Frankhawthorneite is vitreous, brittle and nonfluorescent; H(Mohs) 3-4; D(calc.) 5.43 for the idealized formu la, 5.44, g/cm(3) for the empirical formula. In polished section, fran khawthormeite is weakly bireflectant and nonpleochroic. In reflected p lane-polarized light in air it is pale grey, in oil it is purple-grey, with ubiquitous viridian green internal reflections. The anisotropy i s weak with brown rotation tints. Measured reflectance values, in air and in oil, are tabulated. Electron-microprobe analyses yielded CuO 45 .20, TeO(3)48.77, H2O (calc.) [5.05], total [99.02] wt. %. The empiric al formula, derived from crystal-structure analysis and electron-micro probe analyses, is Cu2.03Te0.996+O4.00(OH)(2.00), based on O = 6 and w ith (OH) = 2.00. The mineral name honors Professor Frank C. Hawthorne, University of Manitoba, for his many important contributions to the f ields of mineralogy and crystallography, and especially for his ongoin g studies of the crystal chemistry of Cu2+ oxysalt minerals.