Håleniusite-(Ce), CeOF, the Ce Analogue of Håleniusite-(La) from the Água de Pau Volcano, Sãn Miguel Island, Azores District, Portugal
Author:
Kampf Anthony R.1, Ma Chi2, Chiappino Luigi3
Affiliation:
1. Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA 2. Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA 3. via Palmanova 67, I-20132 Milano, Italy
Abstract
ABSTRACT
Håleniusite-(Ce) (IMA2021-042), CeOF, is a new mineral discovered in ejectum from the Água de Pau volcano, Sãn Miguel Island, Azores District, Portugal. It occurs as opaque, cream-colored, fine-grained pseudomorphic replacements of hexagonal tablets of bastnäsite-(Ce). It is associated with astrophyllite and fluornatropyrochlore in a matrix composed mainly of albite, quartz, and aegirine. The mineral has a white streak and a calculated density of 5.890 g/cm3 for the empirical formula. The strongest powder diffraction lines are [dobsÅ(Iobs)(hkl)]: 3.247(100)(111), 2.840(31)(200), 2.004(46)(220), and 1.705(42)(311). Electron probe microanalysis provided the empirical formula (Ce0.41La0.21Sm0.15Nd0.04Eu0.03Ca0.02Y0.02Dy0.02Gd0.01)Σ0.91(O0.70F0.30)F1.00. Håleniusite-(Ce) has a fluorite-type structure, space group Fmm, with a = 5.6597(10) Å and V = 181.29(10) Å3 (Z = 4).
Publisher
Mineralogical Association of Canada
Subject
Geochemistry and Petrology
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