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

Frankhawthorneite, ideally Cu2Te6+O4(OH)(2), is monoclinic, P2(1)/n (14), 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) Angstrom(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), 1.713(40)(022) and 1.500(40)(330,231,600). The mineral is found on the dumps 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 drusy white quartz. Associated minerals include mcalpineite, pyrite, hematite, acanthite, chrysocolla, connellite, enargite, hinsdalite, svanbergite and an undefined Cu-Zn-Te-bearing pale green botryoidal crust. Individual crystals of frankhawthomeite are prismatic to stubby bladed, are subhedral to euhedral, and have slightly curved faces. They are elongate [001], with a length-to-width ratio of approximately 3:1. Forms 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 formula, 5.44, g/cm(3) for the empirical formula. In polished section, frankhawthormeite is weakly bireflectant and nonpleochroic. In reflected plane-polarized light in air it is pale grey, in oil it is purple-grey, with ubiquitous viridian green internal reflections. The anisotropy is 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 empirical formula, derived from crystal-structure analysis and electron-microprobe analyses, is Cu2.03Te0.996+O4.00(OH)(2.00), based on O = 6 and with (OH) = 2.00. The mineral name honors Professor Frank C. Hawthorne, University of Manitoba, for his many important contributions to the fields of mineralogy and crystallography, and especially for his ongoing studies of the crystal chemistry of Cu2+ oxysalt minerals.