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Redefinition of Lemanskiite: New Mineralogical Data, Crystal Structure, and Revised Formula NaCaCu5(AsO4)4Cl · 3H2O.
- Source :
- Geology of Ore Deposits; Dec2018, Vol. 60 Issue 7, p594-606, 13p
- Publication Year :
- 2018
-
Abstract
- The crystal structure of lemanskiite is determined for the first time (R = 0.019) and the mineral is redefined. Its chemical formula, crystal system, space group and unit-cell parameters are revised. The powder X-ray diffraction pattern of lemanskiite has been correctly indexed; the IR spectrum of an impurity-free sample has been obtained. It has been shown that the mineral is not a dimorph of lavendulan NaCaCu<subscript>5</subscript>(AsO<subscript>4</subscript>)<subscript>4</subscript>Cl · 5H<subscript>2</subscript>O and differs from the latter by a lower H<subscript>2</subscript>O content. The studied sample was from the oxidation zone of the Perseverancia deposit, Guanako, Antofagasta, Chile. It empirical formula is Na<subscript>0.98</subscript>(Ca<subscript>0.98</subscript>Sr<subscript>0.03</subscript>)Σ<subscript>1.01</subscript>Cu<subscript>5.07</subscript>As<subscript>3.97</subscript>O<subscript>15.97</subscript>Cl<subscript>1.03</subscript> · 3H<subscript>2</subscript>O; the idealized formula is NaCaCu5(AsO4)4Cl · 3H2O. The mineral is monoclinic, P<subscript>2</subscript>1/m, a = 9.250(2), b = 10.0058(10), с = 10.0412(17) Å, β = 97.37(3)°, V = 921.7(3) Å<superscript>3</superscript>, Z =2. Lemanskiite represents a new structure type in the lavendulan group. Its structure is based on heteropolyhedral layers composed of clusters consisting of four edge-shared distorted Cu-centered tetragonal pyramids joined with eight AsO<subscript>4</subscript> tetrahedra, which are also linked with a Cu-centered plane squares not involved in the clusters. Interlayer edge-shared Na-centered trigonal prisms and Ca sevenfold polyhedra are linked with the heteropolyhedral layers from both sides. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 10757015
- Volume :
- 60
- Issue :
- 7
- Database :
- Complementary Index
- Journal :
- Geology of Ore Deposits
- Publication Type :
- Academic Journal
- Accession number :
- 134830264
- Full Text :
- https://doi.org/10.1134/S1075701518070115