JENSENITE, Cu3Te6+O6•2H2O, A NEW MINERAL SPECIES FROM THE CENTENNIAL EUREKA MINE, TINTIC DISTRICT, JUAB COUNTY, UTAH*

ANDREW C. ROBERTS
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8

JOEL D. GRICE
Research Division, Canadian Museum of Nature, Ottawa, Ontario K1P 6P4

LEE A. GROAT
Department of Geological Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia V6T 1Z4

ALAN J. CRIDDLE
Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, U.K.

ROBERT A. GAULT
Research Division, Canadian Museum of Nature, Ottawa, Ontario K1P 6P4

RICHARD C. ERD
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, U.S.A.

ELIZABETH A. MOFFATT
Canadian Conservation Institute, 1030 Innes Road, Ottawa, Ontario K1A 0M5

* Geological Survey of Canada contribution number 68094.

Abstract

Jensenite, ideally Cu3Te6+O6•2H2O, is monoclinic, P21/n (14), with unit-cell parameters refined from powder data: a 9.204(2), b 9.170(2), c 7.584(1) Å, 102.32(3) , V 625.3(3) Å3, a:b:c 1.0037:1:0.8270, Z = 4. The strongest six reflections of the X-ray powder-diffraction pattern [d in Å(I)(hkl)] are: 6.428(100)(01,110), 3.217(70)(02), 2.601(40)(202), 2.530(50)(230), 2.144(35)(31) and 1.750(35)(32). The mineral is found on the dumps of the Centennial Eureka mine, Juab County, Utah, where it occurs as isolated crystals or as groups of crystals on drusy white quartz. Associated minerals are mcalpineite, xocomecatlite and unnamed Cu(Mg,Cu,Fe,Zn)2Te6+O6•6H2O. Individual crystals of jensenite are subhedral to euhedral, and form simple rhombs that are nearly equant. Some crystals are slightly elongate [101], with a length-to-width ratio up to 2:1. The largest crystal is approximately 0.4 mm in size, the average size is between 0.1 and 0.2 mm. Cleavage {01} fair. Forms are: {01} major; {110} medium; {100} minor; {301}, {201}, {203}, {02}, {010} very small. The mineral is transparent, emerald green, with a less intense streak of the same color and an uneven fracture. Jensenite is adamantine, brittle and nonfluorescent; H (Mohs) 3-4; D (calc.) 4.78 for the idealized formula, 4.76 g/cm3 for the empirical formula. In a polished section, jensenite is very weakly bireflectant and nonpleochroic. In reflected plane- polarized light in air, it is a nondescript grey, and in oil, it is a much darker grey with a brownish tint in color, with ubiquitous bright green internal reflections. Anisotropy is not detectable. Measured values of reflectance, in air and in oil, are tabulated. Electron-microprobe analyses yielded CuO 50.91, ZnO 0.31, TeO3 38.91, H2O (calc.) [8.00], total [98.13] wt.%. The empirical formula, derived from crystal-structure analysis and electron-microprobe analyses, is (Cu2.92Zn0.02) 2.94Te01O5.97•2.03H2O, based on O = 8. The mineral name honors Martin C. Jensen, Reno, Nevada, who discovered the mineral.