Goldhillite, Cu₅Zn(AsO₄)₂(OH)₆·H₂O, a new mineral species, and redefinition of philipsburgite, Cu₅Zn[(AsO₄)(PO₄)](OH)₆·H₂O, as an As-P ordered species

Author(s)

Rezeda M. Ismagilova, Branko Rieck, Anthony R. Kampf, Gerald Giester, Elena S. Zhitova, Christian L. Lengauer, Sergey V. Krivovichev, Andrey A. Zolotarev, Justyna Ciesielczuk, Julia A. Mikhailova, Dmitry I. Belakovsky, Vladimir N. Bocharov, Vladimir V. Shilovskikh, Natalia S. Vlasenko, Barbara P. Nash, Paul M. Adams

Abstract

Philipsburgite has been redefined as the intermediate member of the goldhillite–philipsburgite–kipushite isomorphous series with the ideal formula Cu₅Zn[(AsO₄ )(PO₄)](OH)₆⋅H₂O due to the site-selective As–P substitution. The new mineral goldhillite, ideally Cu₅Zn(AsO₄)₂(OH)₆⋅H₂O [or Cu₅Zn(AsO₄)(AsO₄ )(OH)₆⋅H₂O], is the arsenate end-member of this series. Goldhillite occurs on fracture sur-
faces in a rock comprised mostly of quartz with iron hydroxides in association with mixite, cornwallite and conichalcite. Goldhillite forms transparent, bright emerald-green, tabular crystals with vitreous lustre, flattened on {100}, up to 1 mm across and in rosettes up to 1.5 mm. The mineral is brittle with uneven fracture and perfect cleavage on {100}; the Mohs hardness is 3.5. The calculated density for the holotype is 4.199 g cm^–3 . The Raman spectrum is consistent with the presence of H 2 O-molecules, OH-groups, AsO 4 tetrahedra and traces of PO₄. Electron microprobe analyses of goldhillite (H₂O content based on the crystal structure) provided: CuO 48.91, ZnO 13.18, As₂O₅ 26.06, P₂O₅ 3.25, H₂O 8.97, total 100.37 wt.%. The empirical formula for goldhillite based on O = 15 apfu is (Cu_4.69Zn_1.23 )_Σ5.92(As_0.86P_0.18O₄)₂(OH)_5.61⋅H₂O. The crystal structures of goldhillite and philipsburgite were determined using single-
crystal X-ray diffraction data and refined to R1 = 0.054 (for 2365 I > 2σI reflections) and 0.052 (for 2308 I > 2σI reflections), respectively. Goldhillite is monoclinic, P21/c, a = 12.3573(5), b = 9.2325(3), c = 10.7163(4) Å, β = 97.346(4)°, V = 1212.59(8) ų and Z = 4. Philipsburgite is monoclinic, P21/c, a = 12.3095(9), b = 9.2276(3), c = 10.7195(3) Å, β = 97.137(7)°, V = 1208.16(10) ų and Z = 4. The strongest lines of the powder X-ray diffraction pattern of goldhillite [d, Å (I, %)(hkl)] are: 4.09 (28)(300), 3.41 (23)(12 -2, 221, 311), 2.57 (100)(132, 11 -4, 20 -4), 2.17 (18)(42 -3, 332), 1.95 (22)(432) and 1.54 (20)(13 -6, 060). Goldhillite is named after its type locality, the Gold Hill mine, Tooele County, Utah, USA.

Organisation(s)

Department of Mineralogy and Crystallography

External organisation(s)

Saint Petersburg State University, Natural History Museum of Los Angeles County, Russian Academy of Sciences, University of Silesia in Katowice, University of Utah

Journal

Mineralogical Magazine

Volume

86

Pages

436-446

No. of pages

11

ISSN

0026-461X

DOI

https://doi.org/10.1180/mgm.2022.36

Publication date

06-2022

Peer reviewed

Yes

Austrian Fields of Science 2012

104026 Spectroscopy, 105116 Mineralogy, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Geochemistry and Petrology

Portal url

https://ucrisportal.univie.ac.at/en/publications/ab33f233-30c6-4c37-8c1e-b0283de3f94b