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Oldsite, K₂Fe²⁺[(UO₂)(SO₄)₂]₂(H₂O)₈, a new uranyl sulfate mineral from Utah, USA: its description and implications for the formation and occurrences of uranyl sulfate minerals

Plášil, Jakub and Kampf, Anthony R. and Ma, Chi and Desor, Joy (2023) Oldsite, K₂Fe²⁺[(UO₂)(SO₄)₂]₂(H₂O)₈, a new uranyl sulfate mineral from Utah, USA: its description and implications for the formation and occurrences of uranyl sulfate minerals. Mineralogical Magazine, 87 (1). pp. 151-159. ISSN 0026-461X. doi:10.1180/mgm.2022.106.

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Oldsite (IMA2021-075), ideally K₂Fe²⁺[(UO₂)(SO₄)₂]₂(H₂O)₈, is a new uranyl sulfate mineral found on specimens from the North Mesa Mine group, Temple Mountain, San Rafael district, Emery County, Utah, USA. It is a secondary mineral occurring with alum-(K), halotrichite, metavoltine, quartz, römerite, stanleyite, sulphur, szomolnokite and mathesiusite. It forms rectangular blades flattened on {010} and elongated on [001], reaching ~0.3 mm in length. Crystals are yellow in colour, transparent with a vitreous lustre; the streak is very pale yellow. The mineral is non-fluorescent. Cleavage is excellent on {100} and perfect on {010}; the Mohs hardness is ~2. Crystals are brittle with irregular, splintery fracture. The density measured by flotation in a mixture of methylene iodide and toluene is 3.31 g⋅cm⁻³; the calculated density is 3.298 g⋅cm⁻³ for the empirical formula and 3.330 g⋅cm⁻³ for the ideal formula. Oldsite is biaxial (+), with α = 1.552(2), β = 1.556(2) and γ = 1.588(2) (measured in white light). The 2V measured directly on a spindle stage is 37(1)°; the calculated 2V is 39.6°. Dispersion is r < v, moderate. The optical orientation is X = b, Y = a and Z = c. The mineral is non-pleochroic. The empirical formula of oldsite (on the basis of 28 O apfu) is K₁.₉₃(Fe²⁺₀.₅₃Zn₀.₃₁V³⁺₀.₀₉Mg₀.₀₈)_(Σ1.02)[(U₀.₉₈O₂)(S₁.₀₁O₄)₂]₂(H₂O)₈. The Raman spectrum is dominated by the vibrations of SO₄²⁻ and UO₂2²⁺ units. Oldsite is orthorhombic, Pmn2₁, a = 12.893(3), b = 8.276(2), c = 11.239(2) Å, V = 1199.2(5) ų and Z = 2. The five strongest powder X-ray diffraction lines are [d_(obs), Å (I, %) (hkl) ]: 8.29 (59) (010), 6.47 (82) (200), 5.10 (62) (210), 4.65 (100) (012, 211) and 3.332 (55) (022, 221). The crystal structure of oldsite was refined from single-crystal X-ray data to R = 0.0258 for 2676 independent observed reflections, with I_(obs) > 3σ(I). Oldsite is an Fe²⁺ analogue of svornostite; its crystal structure is based upon infinite chains of uranyl-sulfate polyhedra, which comprises pentagonal UO₇ bipyramids sharing four of their equatorial vertices with sulfate tetrahedra such that each tetrahedron is linked to two uranyl bipyramids to form an infinite chain (the free, non-linking equatorial vertex of the uranyl bipyramid is an H₂O group). The broader discussion on the origin and composition of uranyl sulfate minerals is made. The new mineral name honours American mineralogist, Dr. Travis A. Olds for his contribution to uranium mineralogy.

Item Type:Article
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URLURL TypeDescription
Plášil, Jakub0000-0001-6627-5742
Kampf, Anthony R.0000-0001-8084-2563
Ma, Chi0000-0002-1828-7033
Additional Information:© The Author(s), 2022. Published by Cambridge University Press on behalf of The Mineralogical Society of Great Britain and Ireland. This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives licence (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided that no alterations are made and the original article is properly cited. The written permission of Cambridge University Press must be obtained prior to any commercial use and/or adaptation of the article. An anonymous referee, Associate Editor Mike Rumsey and Structure Editor Pete Leverett are highly thanked for their comments that helped improve the manuscript. A portion of this study was funded by the John Jago Trelawney Endowment to the Mineral Sciences Department of the Natural History Museum of Los Angeles County. This research was also financially supported by the Czech Science Foundation (project 20-11949S to JP).
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John Jago Trelawney EndowmentUNSPECIFIED
Czech Science Foundation20-11949S
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ID Code:118937
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Deposited On:22 Feb 2023 19:43
Last Modified:22 Feb 2023 19:43

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