TY - JOUR
T1 - Parisite-(La), ideally CaLa2(CO3)3F2, a new mineral from Novo Horizonte, Bahia, Brazil
AU - Menezes Filho, Luiz A.D.
AU - Chaves, Mario L.S.C.
AU - Chukanov, Nikita V.
AU - Atencio, Daniel
AU - Scholz, Ricardo
AU - Pekov, Igor
AU - Da Costa, Geraldo Magela
AU - Morrison, Shaunna M.
AU - Andrade, Marcelo B.
AU - Freitas, Erico T.F.
AU - Downs, Robert T.
AU - Belakovskiy, Dmitriy I.
N1 - Funding Information:
We acknowledge the Brazilian agencies FAPESP (processes 2014/50819-9 and 2013/03487-8), CNPq, and Finep for financial support, all members of the IMA Commission on New Minerals, Nomenclature and Classification, the Principal Editor Peter Williams, an anonymous reviewer and Fernando Colombo and Peter Leverett for their helpful suggestions and comments. M. Chaves thanks CNPq (grant No. 305492/2013-6) and R. Scholz thanks CNPq and FAPEMIG (respectively grant No. 305284/2015-0 and grant APQ-01448-15).
Publisher Copyright:
© 2018 Mineralogical Society of Great Britain and Ireland.
PY - 2018/2/1
Y1 - 2018/2/1
N2 - 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).
AB - 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).
KW - Bahia
KW - Brazil
KW - Mula mine
KW - Novo Horizonte
KW - new mineral
KW - parisite-(La)
KW - rare-earth fluorocarbonate
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U2 - 10.1180/minmag.2017.081.028
DO - 10.1180/minmag.2017.081.028
M3 - Article
AN - SCOPUS:85047886571
VL - 82
SP - 133
EP - 144
JO - Mineralogical Magazine
JF - Mineralogical Magazine
SN - 0026-461X
IS - 1
ER -