IMA 2020-078 = nitscheite

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Marco E. Ciriotti
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IMA 2020-078 = nitscheite

Messaggio da Marco E. Ciriotti » gio 01 lug, 2021 19:44

Prossima pubblicazione.

Referenza:
▪ Kampf, A.R., Olds, T.A., Plášil, J., Nash, B.P., Marty, J. (2021): Nitscheite, (NH4)2[(UO2)2(SO4)3(H2O)2]·3H2O, a new mineral with an unusual uranyl-sulfate sheet. American Mineralogist, 106, (in press).

Abstract:
Nitscheite (IMA2020-078), (NH4)2[(UO2)2(SO4)3(H2O)2]·3H2O, is a new mineral species from the Green Lizard mine, Red Canyon, San Juan County, Utah, U.S.A. It is a secondary phase found in association with chinleite-(Y), gypsum, pyrite, and Co-rich rietveldite. Nitscheite occurs in subparallel and divergent intergrowths of yellow prisms, up to about 0.3 mm in length. Crystals are elongated on [101] and exhibit the forms {100}, {010}, {001}, and {11-1}. The mineral is transparent with vitreous luster and very pale-yellow streak. It exhibits bright green fluorescence under a 405 nm laser. The Mohs hardness is ~2. The mineral has brittle tenacity, curved fracture, and one good cleavage on {010}. The measured density is 3.30(2) g·cm-3. The mineral is easily soluble in RT H2O. The mineral is optically biaxial (-), α = 1.560(2), β = 26 1.582(2), γ = 1.583(2) (white light); 2Vmeas = 17(1)°; no dispersion; orientation X = b, Z ≈ [101]; pleochroism X colourless, Y and Z yellow; X < Y ≈ Z. Electron microprobe analysis provided the empirical formula (NH4)1.99U2.00S3.00O21H10.01. Nitscheite is monoclinic, P21/n, a = 17.3982(4), b = 12.8552(3), c = 17.4054(12) Å, β = 96.649(7)°, V = 3866.7(3) Å 3 , and Z = 8. The structure (R1 = 0.0329 for 4547 I > 3sigma(I) reflections) contains [(UO2)2(SO4)3(H2O)2]2- uranyl-sulfate sheets, which are unique among minerals, with NH4 and H2O groups between the sheets.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 28447
Iscritto il: ven 25 giu, 2004 11:31
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Re: IMA 2020-078 = nitscheite

Messaggio da Marco E. Ciriotti » gio 22 lug, 2021 13:55

Abstract aggiunto. Grazie Joe!
Marco E. Ciriotti

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