Journal of


  (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


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) Å3, 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.  

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