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

Abstract

Krupičkaite, ideally Cu 6 [AsO 3 (OH)] 6 •8H 2 O, is a new supergene mineral from the Rovnost I shaft in Jáchymov, Czech Republic. It forms aggregates of pale greenish-blue 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) Å 3 , Z = 4, space group P2 1 /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 copper-arsenate sheets stacked along b presenting a characteristic wave shape along the a-axis and separated by a thick interlayer with channels containing only H 2 O. The collapsed chains of copper polyhedra are connected the same way as in geminite through AsO 4 tetrahedra. Krupičkaite joins the family of copper arsenate minerals with which it shares structural similarities at the level of the As-Cu layers with the lindackerite supergroup, slavkovite, or yvonite.

Dobšináite, Ca2Ca(AsO4)2·2H2O, a new member of the roselite group from Dobšiná (Slovak Republic)

“…During our long-term systematic mineralogical research focused on supergene arsenate minerals from various occurrences (Sejkora et al 1999(Sejkora et al , 2009(Sejkora et al , 2018Plumhoff et al 2020;Steciuk et al 2021), dobšináite, a new Ca dominant member of the roselite group, was discovered; in this paper, we report its description. Arsenate members of the roselite group comprise monoclinic minerals of generalized composition Ca 2 M(AsO 4 ) 2 •2H 2 O.…”

New Mineral Names: Alteration Products

“…Krupičkaite (Steciuk et al 2021), ideal Cu 6 [AsO 3 (OH)] 6 •8H 2 O, is named after Prof. Jirí Krupička who was a geologist, linguist, and astronomer in Prague. Prof. Krupička was a labor camp survivor and was imprisoned for writing a manuscript denouncing the nuclear arms race.…”

Grandviewite redefinition, new formula Cu3Al2(SO4)(OH)10⋅H2O, and crystal-structure determination

“…The sample was crushed in a mortar without solvent and deposited on a Au-grid coated by a thin film of holey amorphous carbon. To preserve the hydrated structure of the mineral under the high vacuum in the TEM, the grid was plunged into liquid nitrogen and transferred to the TEM using a Gatan 626 cryo-transfer holder (Gemmi et al , 2019; Mugnaioli et al , 2020; Steciuk et al , 2021a, 2021b). The PEDT technique was chosen to collect stepwise 3D ED data at 100 K. For each selected crystal area (Fig.…”