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Tinsleyite in the " dry " Cioclovina Cave (Sureanu Mountains, Romania): the second occurrence

Abstract : This paper documents the occurrence of tinsleyite in the "dry" Cioclovina Cave, Sureanu Mountains, Romania. This is the first mention of tinsleyite as a cave mineral and the second find of this mineral species in the world. The mineral occurs in small quantities, as a rare authigenic, early diagenetic mineral, in the bat guano deposits in this cave. Low (alpha) quartz is the only closely associated mineral. This assemblage corresponds to a possible reaction in the natural guano - clay system upon decomposition of illite. Chemical analyses show variable leucophosphite contents (up to 31.68 mol.%). The unit-cell parameters calculated for an iron-poor sample are a = 9.638(5) Å, b = 9.522(4) Å, c = 9.540(4) Å and ß = 103.10(3)°, whereas those determined for an iron-rich sample are a = 9.639(6) Å, b = 9.538(8) Å, c= 9.553(7) Å and ß = 103.04(4)°. Thermal analyses show that water is lost in three steps and that the loss of molecular water is complete before 250°C. The fully dehydrated material is completely X-ray amorphous. Ammonium is expelled at about 490°C. The infrared spectrum of tinsleyite affords reasonable evidence for the presence of PO4, NH4 and OH groups, together with H2O molecules. The punctual symmetry of the PO4 groups is Cs.
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Submitted on : Wednesday, August 3, 2011 - 11:15:19 AM
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Stefan Marincea, Delia Dumitras, Raymonde Gibert. Tinsleyite in the " dry " Cioclovina Cave (Sureanu Mountains, Romania): the second occurrence. European Journal of Mineralogy, Copernicus, 2002, 14 (1), pp.157-164. ⟨10.1127/0935-1221/2002/0014-0157⟩. ⟨emse-00613171⟩



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