Parisite-(La), ideally CaLa2(CO3)3F2, a new mineral from Novo Horizonte, Bahia, Brazil

Luiz A.D. Menezes Filho, Mario L.S.C. Chaves, Nikita V. Chukanov, Daniel Atencio, Ricardo Scholz, Igor Pekov, Geraldo Magela Da Costa, Shaunna M. Morrison, Marcelo B. Andrade, Erico T.F. Freitas, Robert T Downs, Dmitriy I. Belakovskiy

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Parisite-(La) (IMA2016-031), ideally CaLa2(CO3)3F2, occurs in a hydrothermal vein crosscutting a metarhyolite of the Rio dos Remédios Group, at the Mula mine, Tapera village, Novo Horizonte county, Bahia, Brazil, associated with hematite, rutile, almeidaite, fluocerite-(Ce), brockite, monazite-(La), rhabdophane-(La) and bastnäsite-(La). Parisite-(La) occurs as residual nuclei (up to 5 mm) in steep doubly-terminated pseudo-hexagonal pyramidal crystals (up to 8.2 cm). Parisite-(La) is transparent, yellow-green to white, with a white streak and displays a vitreous (when yellow-green) to dull (when white) lustre. Cleavage is distinct on pseudo-{001}; fracture is laminated, conchoidal, or uneven. The Mohs hardness is 4 to 5, and it is brittle. Calculated density is 4.273 g cm-3. Parisite-(La) is pseudo-uniaxial (+), ω = 1.670(2) and ϵ = 1.782(5) (589 nm). The empirical formula normalized on the basis of 11 (O + F) atoms per formula unit (apfu) is Ca0.98(La0.83Nd0.51Ce0.37Pr0.16Sm0.04Y0.03)Σ1.94C3.03O8.91F2.09. The IR spectrum confirms the absence of OH groups. Single-crystal X-ray studies gave the following results: monoclinic (pseudo-trigonal), space group: C2, Cm, or C2/m, a = 12.356(1) Å, b = 7.1368(7) Å, c = 28.299(3) Å, β = 98.342(4)°, V = 2469.1(4) Å3 and Z = 12. Parisite-(La) is the La-dominant analogue of parisite-(Ce).

Original languageEnglish (US)
Pages (from-to)133-144
Number of pages12
JournalMineralogical Magazine
Volume82
Issue number1
DOIs
StatePublished - Feb 1 2018

Keywords

  • Bahia
  • Brazil
  • Mula mine
  • new mineral
  • Novo Horizonte
  • parisite-(La)
  • rare-earth fluorocarbonate

ASJC Scopus subject areas

  • Geochemistry and Petrology

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    Menezes Filho, L. A. D., Chaves, M. L. S. C., Chukanov, N. V., Atencio, D., Scholz, R., Pekov, I., Da Costa, G. M., Morrison, S. M., Andrade, M. B., Freitas, E. T. F., Downs, R. T., & Belakovskiy, D. I. (2018). Parisite-(La), ideally CaLa2(CO3)3F2, a new mineral from Novo Horizonte, Bahia, Brazil. Mineralogical Magazine, 82(1), 133-144. https://doi.org/10.1180/minmag.2017.081.028