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Mineralogical ClassificationIMA2018-110 = Nickeltyrrellite published

13th Sep 2019 08:28 UTCKnut Edvard Larsen 🌟 Manager

Fürster, H.-J., Ma, C. Grundmann, G., Bindi, L. & Stanley . c. J. (2019) Nickeltyrrellite, CuNi2Se4, a New Member of the Spinel Supergroup from El Dragón, Bolivia. The Canadian Mineralogist (2019) canmin.1900025. https://doi.org/10.3749/canmin.1900025

Abstract:

Nickeltyrrellite, ideally CuNi2Se4, is a new selenide species from the El Dragón mine, Department of Potosí, Bolivia. It most frequently occurs as anhedral to subhedral grains (up to 20 μm in size) in association with cerromojonite, klockmannite, clausthalite, and penroseite, forming fracture fillings in pre-existing krut'aite−penroseite solid solutions. Nickeltyrrellite is non-fluorescent, black, and opaque with a metallic luster and black streak. It is brittle, with an irregular fracture and no obvious cleavage and parting. In plane-polarized incident light, nickeltyrrellite is cream to pale pinkish, displaying no internal reflections. Between crossed polarizers, it is isotropic. The reflectance values in air for the COM standard wavelengths are 45.9 (470 nm), 47.6 (546 nm), 48.1 (589 nm), and 49.8 (650 nm). Electron-microprobe spot analyses (n = 28) of the grain populations used for the EBSD study yielded a mean composition of Cu 13.01, Fe 0.27, Co 6.66, Ni 16.98, S 1.04, Se 61.91, total 99.87 wt.%. The empirical formula, normalized to 7 apfu, is Cu1.00(Ni1.42Co0.56Fe0.02)Σ2.00(Se3.84S0.16)Σ4.00. The ideal formula is CuNi2Se4, which requires (in wt.%) Cu 12.79, Ni 23.63, Se 63.58, total 100. EBSD patterns reveal nickeltyrrellite as cubic, space group Fd-3m with a = 9.99 Å, V = 997.0 Å3, Z = 8. The calculated density is 7.36 g cm−3. It formed in response to alteration of quijarroite + hansblockite + watkinsonite + clausthalite + penroseite aggregates by oxidizing, low-T, Cu-Ni-Co-Pb-bearing fluids at a fSe2/fS2 ratio greater than unity. Nickeltyrrellite is a new selenide belonging to the tyrrellite subgroup of the spinel supergroup. The new species has been approved by the IMA-CNMNC (2018-110) and is named for constituting the Ni-analogue of tyrrellite

https://pubs.geoscienceworld.org/canmin/article-abstract/573439/nickeltyrrellite-cuni2se4-a-new-member-of-the?redirectedFrom=fulltext

Mineral and locality page updated.

13th Sep 2019 09:50 UTCDr. Günter Grundmann 🌟 Expert

Hi Knut,

please correct the name of the first author as Förster instead of "Fürster".

Many thanks for your efforts,

Best, Guenter

13th Sep 2019 12:34 UTCKnut Edvard Larsen 🌟 Manager

Thanks Günter, I saw it after posting it, but I was not able to correct it in the bluish-green field above.
It is however correct on the mineral and locality pages.

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