Crystal structure and crystal chemical features of a new, discovered in fumaroles of the Tolbachik volcano (Kamchatka) copper and potassium hydroxychloride - romanorlovite, with the simplified formula K 11 Cu 9 Cl 25 (OH) 4 ∙2H 2 O (Z = 4), are reported. The mineral is tetragonal, I4/mmm, a = 17.5538(19), c = 15.8620(17) Å, V = 4887.7(9) Å 3 . The structure was determined using single-crystal XRD data and refined to R = 5.49 % for 769 unique reflections with I > 2s(I). The structure is based on two main blocks built by Cu 2+ -centere polyhedra. The first one includes chains consisting of edge-sharing CuCl 4 (OH) 2 octahedra. In the chain a fragment built by four edge-sharing Cu(1)-centered octahedral could be distinguished whereas Cu(2)-centered octahedra are connected with this fragment from both upper and lower sides. The second structural block consists of isolated Cu 6 Cl 18 clusters built by Cu(3)-centered tetragonal pyramids and Cu(4)-centered distorted tetrahedra. In a core of the cluster Cu2+ and Pb2+ cations statistically replacing each other in the same site are located. Two these basic structural blocks are connected via distorted ACl 6 octahedra (A = Cu, K) forming pseudo-framework. K+ cations are located in the voids and channels of the pseudo-framework. Romanorlovite has the crystal-chemical formula K 24 (K,Pb) 16 (K,Cu,□) 8 Cu 28 (□,Cu) 16 (□,Cu,Pb) 2 Cl 92 $ (Cl,9) 8 (9,Cl) 8 (OH) 16 ∙8H 2 O (Z = 1). Various defects revealed in its structure are discussed.
|Журнал||Zapiski Rossiiskogo Mineralogicheskogo Obshchestva|
|Состояние||Опубликовано - 1 янв 2016|
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