Title

Hydroxylellastadite from Cioclovina Cave (Romania), Microanalytical, Structural, and Vibrational Spectroscopy Data

Document Type

Article

Publication Date

2006

Keywords

Hydroxylellestadite, britholite group, bat guano combustion, cave minerals, Cioclovina Cave, Romania

Digital Object Identifier (DOI)

http://dx.doi.org/10.2138/am.2006.2143

Abstract

Electron-microprobe analyses of hydroxylellestadite from the Cioclovina Cave (Romania) gave the composition Ca10.27[(SiO4)2.53(SO4)2.17(PO4)1.27]∑=5.97[(OH)1.66F0.21Cl0.16]∑=2.03. The mineral is translucent to transparent, light orange, slightly fluorescent, has a vitreous luster and <1.5 mm in length. A single-crystal X-ray structure investigation gave the average space-group symmetry P63/m [R1(F) = 0.038 for 783 reflections up to 2�MoKα = 70° and 42 variables, a = 9.496(2), c = 6.920(2) Å, V = 540.4 Å3, and Z = 2]. Some atoms exhibit large anisotropic displacements. Ordering of atoms along with a symmetry reduction is not verified. Fourier-transformed infrared (FT-IR) and micro-Raman spectra exhibit a distinct contribution from (PO4)3− modes along with the characteristic (SO4)2− and (SiO4)4− modes. The occurrence is quite unusual and suggests that an intense thermal process affected a restricted area within the cave. Hydroxylellestadite is associated with berlinite, another high-temperature mineral. It is likely to have formed within highly phosphatized, silicate-rich, carbonate-mudstone sediments heavily compacted and thermally transformed due to in situ bat guano combustion.

Citation / Publisher Attribution

American Mineralogist, v. 91, no. 11-12, p. 1927-1931

Was this content written or created while at USF?

Yes