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Type: Journal article
Title: Xocolatlite, Ca₂Mn₂⁴⁺Te₂O₁₂·H₂O, a new tellurate related to kuranakhite: Description and measurement of Te oxidation state by XANES spectroscopy
Other Titles: Xocolatlite, Ca2Mn24+Te2O12 center dot H2O, a new tellurate related to kuranakhite: Description and measurement of Te oxidation state by XANES spectroscopy
Author: Grundler, P.
Brugger, J.
Meisser, N.
Ansermet, S.
Borg, S.
Etschmann, B.
Testemale, D.
Bolin, T.
Citation: American Mineralogist: an international journal of earth and planetary materials, 2008; 93(11-12):1911-1920
Publisher: Mineralogical Soc Amer
Issue Date: 2008
ISSN: 0003-004X
Statement of
Pascal V. Grundler, Joël Brugger, Nicolas Meisser, Stefan Ansermet, Stacey Borg, Barbara Etschmann, Denis Testemale and Trudy Bolin
Abstract: Xocolatlite, Ca2Mn24+ Te26+ O12·H2O, is a rare new mineral from the Moctezuma deposit in Sonora, Mexico. It occurs as chocolate-brown crystalline crusts on a quartz matrix. Xocolatlite has a copper-brown streak, vitreous luster, and is transparent. Individual crystals show a micaceous habit. Refractive indices were found to be higher than 2.0. Density calculated from the empirical formula is 4.97 g/cm3, and immersion in Clerici solution indicated a density higher than 4.1 g/cm3. The mineral is named after the word used by the Aztecs for chocolate, in reference to its brown color and provenance. The crystallographic characteristics of this monoclinic mineral are space group P2, P2/m, or Pm, with the following unit-cell parameters refined from synchrotron X-ray powder diffraction data: a = 10.757(3) Å, b = 4.928(3) Å, c = 8.942(2) Å, β = 102.39(3)°, V = 463.0(3) Å, and Z = 2. The unavailability of a suitable crystal prevented single-crystal X-ray studies. The strongest 10 lines of the X-ray powder diffraction pattern are [d in Å (I) (hkl)]: 3.267(100)(012), 2.52(71)(303̄), 4.361(51) (002), 1.762(39)(323̄), 4.924 (34)(010), 2.244(32)(313̄), 1.455(24)(006), 1.996(21)(014), 1.565(20) (611), and 2.353(18)(411̄). XANES Te Lm-edge spectra of a selection of Te minerals (including xocolatlite) and inorganic compounds showed that the position of the absorption edge can be reliably related to the oxidation state of Te. XANES demonstrated that xocolatlite contains Te6+ as a tellurate group. Water has been tentatively included in the formula based on IR spectroscopy that indicated the presence of a small amount of water. Raman, IR, XANES, and X-ray diffraction data together with the chemical composition show a similarity of xocolatlite to kuranakhite. A possible series may exist between these two species, xocolatlite being the Ca-rich end-member and kuranakhite the Pb-rich one.
Keywords: Xocolatlite
new mineral
XANES spectroscopy
tellurium oxidation state
Rights: © 2008 Mineralogical Society of America
DOI: 10.2138/am.2008.2870
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Appears in Collections:Aurora harvest 5
Earth and Environmental Sciences publications

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