Revisiting the structure of uranyl arsenate mineral hügelite provided some corrections to the available structural data. The previous twinning model (by reticular merohedry) in hügelite has been corrected. Twinning of the monoclinic unit cell [a = 7.0189 (7) Å, b = 17.1374 (10) Å, c = 8.1310 (10) Å and β = 108.904 (10)°], which can be expressed as a mirror in [100], leads to a pseudo-orthorhombic unit cell (a = 7.019 Å, b = 17.137 Å, c = 61.539 Å and β = 90.02°), which is eight times larger, with respect to the unit-cell volume, than a real cell. Moreover, the unit cell of chosen here and the unit cell given by the previous structure description both lead to the same supercell. A new structure refinement undertaken on an untwinned crystal of hügelite resulted in R = 4.82% for 12 864 reflections with Iobs > 3σ(I) and GOF = 1.12. The hydrogen-bonding scheme has been proposed for hügelite for the first time.

Department of Mineralogy and Petrology National Museum Cirkusová 1740 Praha 9 19300 Czech Republic

Institute of Physics ASCR v v i Na Slovance 2 Praha 8 18221 Czech Republic

See more in PubMed

Brown, I. D. (2002). The Chemical Bond in Inorganic Chemistry: The Bond Valence Model, p. 278. Oxford University Press.

Brown, I. D. (2009). Chem. Rev. 109, 6858–6919. PubMed PMC

Burns, P. C. (2005). Can. Mineral. 43, 1839–1894.

Dürrfeld, V. (1913). Z. Krystallogr. Mineral. 51, 278–279.

Finch, R. J. & Murakami, T. (1999). Reviews in Mineralogy, Vol. 38, Uranium: Mineralogy, Geochemistry and the Environment, edited by P. C. Burns & R. Finch, pp. 91–179. Chantilly, VA: Mineralogical Society of America and Geochemical Society.

Gagné, O. C. & Hawthorne, F. C. (2015). Acta Cryst. B71, 562–578. PubMed PMC

Gorman-Lewis, D., Shvareva, T., Kubatko, K. A., Burns, P. C., Wellman, D. M., McNamara, B., Szymanowski, J. E. S., Navrotsky, A. & Fein, J. B. (2009). Environ. Sci. Technol. 43, 7416–7422. PubMed

Krivovichev, S. V. & Plášil, J. (2013). Uranium, from cradle to grave, MAC Short Course series, Vol. 43, edited by P. C. Burns & G. E. Sigmon, pp. 15–119. Québec: Mineralogical Association of Canada.

Locock, A. J. & Burns, P. C. (2003). Mineral. Mag. 67, 1109–1120.

Lussier, A. J., Lopez, R. A. K. & Burns, P. C. (2016). Can. Mineral. 54, 177–283.

Maher, K., Bargar, J. R. & Brown, G. E. Jr (2013). Inorg. Chem. 52, 3510–3532. PubMed

Petříček, V., Dušek, M. & Palatinus, L. (2014). Z. Kristallogr. 229, 345–352.

Petříček, V., Dušek, M. & Plášil, J. (2016). Z. Kristallogr. 231, 583–599.

Piret, P. & Piret-Meunier, J. (1988). Bull. Minéral. 111, 439–442.

Plášil, J. (2014). J. Geosci. 59, 99–114.

Plášil, J., Kiefer, B., Ghazisaeed, S. & Philippo, S. (2020). Acta Cryst. B76, 502–509. PubMed PMC

Rigaku (2019). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Yarnton, Oxfordshire, England.

Schindler, M. & Hawthorne, F. C. (2008). Can. Mineral. 46, 467–501.

Sheldrick, G. M. (2015). Acta Cryst. A71, 3–8. PubMed

Vochten, R. & Goeminne, A. (1984). Phys. Chem. Miner. 11, 95–100.

Walenta, K. (1979). Tschermaks Mineral. Petrogr. Mitt. 26, 11–19.

Walenta, K. & Wimmenauer, W. (1961). Jahresh. Geol. Landesamtes Baden-Wuerttemb. 4, 7–37.

Hidden and apparent twins in uranyl-oxide minerals agrinierite and rameauite: a demonstration of metric and reticular merohedry