IMA 2018-141 = andymcdonaldite

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Marco E. Ciriotti
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IMA 2018-141 = andymcdonaldite

Messaggio da Marco E. Ciriotti » mer 06 nov, 2019 12:25

Prossima pubblicazione.

▪ Coolbaugh, M.F., McCormack, J.K., Raudsepp, M., Czech, E., McMillan, R., Kampf, A.R. (2019): Andymcdonaldite, (Fe3+2Te6+O6), a new ferric iron tellurate with inverse trirutile structure from the Detroit District, Juab Country, Utah. Canadian Mineralogist, 57, (in press).

Andymcdonaldite is a new ferric-iron-tellurate mineral that occurs within Au-, Te-, and Bi-rich jasperoid at the Wildcat prospect in the Detroit district, Juab County, Utah. The mineral has a yellow-brown to brownish-black color and occurs as extremely cryptocrystalline (11-25 nm) material in thin films and breccia matrix fillings, and is associated with gold (native), tellurium (native), beyerite, clinobisvanite, and a variety of tellurium oxysalt minerals that include carlfriesite, eckhardite, frankhawthorneite, khinite, mcalpinite, paratellurite, tellurite, tlapallite, and xocolatlite. Its natural occurrence is the first known for a phase with an ordered (tetragonal) inverse trirutile structure (A3+2B6+O6) that otherwise has many synthetic representatives. The B site in andymcdonaldite is occupied by Te and the A site is dominated by Fe with up to approximately 14% substitution by other cations. An empirical formula of (Fe1.74Cu0.12Mn0.06Al0.05Mg0.05)Σ2.02Te1.01O6 was obtained from electron microprobe analyses. Powder x-ray diffraction data, Raman spectra, and unit-cell dimensions for andymcdonaldite strongly resemble those for the synthetic analogue, Fe3+2Te6+O6. The strongest X-ray diffraction lines are [dobsÅ(Iobs)(hkl)]: 4.14(27)(101), 3.28(100)(110), 2.54(71)(103), 1.71(72)(213), and 1.37(39)(303,116). The strongest Raman bands are at 748, 643, and 417 cm-1. The cell dimensions are a = 4.622-4.630 Å, c = 9.077-9.087 Å, and V = 193.94-194.80 Å3 (Z = 2).
Marco E. Ciriotti

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