Klajite, MnCu4(AsO4)2(AsO3OH)2(H2O)10, the Mn-Cu-bearing member of the lindackerite group, was found in Jáchymov, Czech Republic, as the second world occurrence. The crystal structure was refined to R1 = 0.0628 for 1034 unique observed reflections, confirming that klajite (Mn-Cu member) and ondrušite (Ca-Cu member of the lindackerite group) are isostructural.
The current data-set allowed determination of the positions of several hydrogen atoms. Discussion on hydrogen bonding networks in the structure of klajite as well as detailed bond-valence analysis are provided.