Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original paper

Gwladys Steciuk, Jiří Sejkora, Jiří Čejka, Jakub Plášil, Jan Hloušek

Krupičkaite, Cu₆[AsO₃(OH)]₆·8H₂O, a new copper arsenate mineral from Jáchymov (Czech Republic)

Journal of Geosciences, volume 66 (2021), issue 1, 37 - 50

DOI: http://doi.org/10.3190/jgeosci.318

Krupičkaite, ideally Cu₆[AsO₃(OH)]₆·8H₂O, is a new supergene mineral from the Rovnost I shaft in Jáchymov, Czech Republic. It forms aggregates of pale bluish-green color and grows along with supergene minerals crystallizing on the strongly altered relics of massive tennantite, Bi-rich tennantite, galena, chalcopyrite, bornite, and chalcocite with disseminated uraninite in quartz. For a long time, krupičkaite has been left out due to its quite inconspicuous ap¬pearance that can be mistakenly referred to as geminite. At the ambient temperature, krupičkaite is monoclinic, a = 15.504(7) Å, b = 18.144(7) Å, c = 10.563(5) Å, β = 103.30(4)°, V = 2891.5(2) ų, Z = 4, space group P2₁/m. Its structure has been solved and refined from 3D electron diffraction and further studied by Raman spectroscopy. The layered structure is built upon the alternation of two different cooper-arsenate sheets stacked along b presenting a characteristic wave shape along the a-axis and separated by a thick interlayer with channels containing only H₂O. The collapsed chains of cooper polyhedra are connected the same way as in geminite through AsO₄ tetrahedra. Krupičkaite joins the family of cooper arsenate minerals with which it shares structural similarities at the level of the As-Cu layers with the lindackerite supergroup, slavkovite, or yvonite.