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Joëlbruggerite, Pb₃Zn₃(Sb⁵⁺,Te⁶⁺)As₂O₁₃(OH,O), the Sb⁵⁺ analog of dugganite, from the Black Pine mine, Montana

¹ Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia V6T 1Z4, Canada
² Mineralogisch-Petrographische Abteilung, Naturhistorisches Museum Wien, Burgring 7, A-1010 Wien, Austria
³ Department of Geology, National Museum of Nature and Science, 3-23-1, Hyakunin-cho, Shinjuku, Tokyo 169-0073, Japan
⁴ Mineral Sciences Division, Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, Ontario K1P 6P4, Canada

Correspondence: ^* E-mail: smills{at}eos.ubc.ca

Joëlbruggerite, ideally Pb₃Zn₃(Sb⁵⁺,Te⁶⁺)As₂O₁₃(OH,O), is a new arsenate mineral (IMA 2008-034) and the Sb⁵⁺ analog of dugganite, from the Black Pine mine, 14.5 km northwest of Philipsburg, Granite County, Montana. It is usually found perched on mimetite; other species that may be present include malachite, azurite, pseudomalachite, chalcocite, beudantite-corkite, duftite, dugganite, and kuksite, in milky quartz veins. Joëlbruggerite occurs as barrel-shaped or prismatic crystals up to about 50 µm across in various shades of purple. The crystals have an adamantine luster and a white streak. Mohs hardness is about 3. The fracture is irregular, and the tenacity is brittle. Joëlbruggerite crystals are uniaxial (–), with a calculated refractive index of n = 1.993, and weakly pleochroic: X = Y = gray, Z = purple; absorption: Z > X = Y. Crystals show straight extinction and are length-fast. The empirical chemical formula (mean of 5 electron microprobe analyses) calculated on the basis of 14 [O + OH] anions is Pb_3.112(Zn_2.689Fe_0.185²⁺)_2.874(Sb_0.650⁵⁺Te_0.451⁶⁺)_1.101(As_1.551P_0.203Si_0.160)1.914O_13.335(OH)_0.665. Joëlbruggerite is trigonal, space group P321, a = 8.4803(17), c = 5.2334(12) Å, V = 325.94(12) ų, Z = 1. The five strongest lines in the powder X-ray diffraction pattern are [d_obs in Å (I) (hkl)]: 3.298 (100) (111), 3.008 (89) (021), 1.905 (39) (122, 131), 2.456 (36) (012, 121, 030), and 1.609 (30) (112, 132, 231, 140). The crystal structure was solved from single-crystal X-ray diffraction data and refined to R₁ = 0.038 on the basis of 604 unique reflections with F > 4(F). It is composed of heteropolyhedral sheets of edge-sharing (Sb,Te)O₆ octahedra and PbO₈ disphenoids, oriented parallel to (001). The sheets are cross-linked by AsO₄ and ZnO₄ tetrahedra, which share corners to form an interlinked, two- and three-connected two-dimensional net parallel to (001). The mineral is named for Joël Brugger (born 1967), Swiss-Australian mineralogist, for his contributions to mineralogy.

Key Words: Joëlbruggerite • new mineral • Sb⁵⁺ • arsenate • Black Pine mine • dugganite • crystal structure • bond valence