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Waimirite-(Y), orthorhombic YF (sub 3) , a new mineral from the Pitinga Mine, Presidente Figueiredo, Amazonas, Brazil and from Jabal Tawlah, Saudi Arabia; description and crystal structure

Daniel Atencio, Artur C. Bastos Neto, Vitor P. Pereira, Jose T. M. M. Ferron, M. Hoshino, T. Moriyama, Y. Watanabe, R. Miyawaki, Jose M. V. Coutinho, Marcelo B. Andrade, Kenneth Domanik, Nikita V. Chukanov, K. Momma, H. Hirano and M. Tsunematsu
Waimirite-(Y), orthorhombic YF (sub 3) , a new mineral from the Pitinga Mine, Presidente Figueiredo, Amazonas, Brazil and from Jabal Tawlah, Saudi Arabia; description and crystal structure
Mineralogical Magazine (June 2015) 79 (3): 767-780

Abstract

Waimirite-(Y) (IMA 2013-108), orthorhombic YF (sub 3) , occurs associated with halloysite, in hydrothermal veins (up to 30 mm thick) cross-cutting the albite-enriched facies of the A-type Madeira granite ( approximately 1820 Ma), at the Pitinga mine, Presidente Figueiredo Co., Amazonas State, Brazil. Minerals in the granite are 'K-feldspar', albite, quartz, riebeckite, 'biotite', muscovite, cryolite, zircon, polylithionite, cassiterite, pyrochlore-group minerals, 'columbite', thorite, native lead, hematite, galena, fluorite, xenotime-(Y), gagarinite-(Y), fluocerite-(Ce), genthelvite-helvite, topaz, 'illite', kaolinite and 'chlorite'. The mineral occurs as massive aggregates of platy crystals up to approximately 1 mu m in size. Forms are not determined, but synthetic YF (sub 3) displays pinacoids, prisms and bipyramids. Colour: pale pink. Streak: white. Lustre: non-metallic. Transparent to translucent. Density (calc.) = 5.586 g/cm (super 3) using the empirical formula. Waimirite-(Y) is biaxial, mean n=1.54-1.56. The chemical composition is (average of 24 wavelength dispersive spectroscopy mode electron microprobe analyses, O calculated for charge balance): F 29.27, Ca 0.83, Y 37.25, La 0.19, Ce 0.30, Pr 0.15, Nd 0.65, Sm 0.74, Gd 1.86, Tb 0.78, Dy 8.06, Ho 1.85, Er 6.38, Tm 1.00, Yb 5.52, Lu 0.65, O (2.05), total (97.53) wt.%. The empirical formula (based on 1 cation) is (Y (sub 0.69) Dy (sub 0.08) Er (sub 0.06) Yb (sub 0.05) Ca (sub 0.03) Gd (sub 0.02) Ho (sub 0.02) Nd (sub 0.01) Sm (sub 0.01) Tb (sub 0.01) Tm (sub 0.01) Lu (sub 0.01) ) (sub Sigma 1.00) [F (sub 2.54) [] (sub 0.25) O (sub 0.21) ] (sub Sigma 3.00) . Orthorhombic, Pnma, a=6.386(1), b=6.877(1), c=4.401(1) Aa, V=193.28(7) Aa (super 3) , Z=4 (powder data). Powder X-ray diffraction (XRD) data [d in Aa (I) (hkl)]: 3.707 (26) (011), 3.623 (78) (101), 3.438 (99) (020), 3.205 (100) (111), 2.894 (59) (210), 1.937 (33) (131), 1.916 (24) (301), 1.862 (27) (230). The name is for the Waimiri-Atroari Indian people of Roraima and Amazonas. A second occurrence of waimirite-(Y) is described from the hydrothermally altered quartz-rich microgranite at Jabal Tawlah, Saudi Arabia. Electron microprobe analyses gave the empirical formula (Y (sub 0.79) Dy (sub 0.08) Er (sub 0.05) Gd (sub 0.03) Ho (sub 0.02) Tb (sub 0.01) Tm (sub 0.01) Yb (sub 0.01) ) (sub Sigma 1.00) [F (sub 2.85) O (sub 0.08) [] (sub 0.07) ] (sub Sigma 3.00) . The crystal structure was determined with a single crystal from Saudi Arabia. Unit-cell parameters refined from single-crystal XRD data are a=6.38270(12), b=6.86727(12), c=4.39168(8) Aa, V=192.495(6) Aa (super 3) , Z=4. The refinement converged to R (sub 1) =0.0173 and wR (sub 2) =0.0388 for 193 independent reflections. Waimirite-(Y) is isomorphous with synthetic SmF (sub 3) , HoF (sub 3) and YbF (sub 3) . The Y atom forms a 9-coordinated YF (sub 9) tricapped trigonal prism in the crystal structure. The substitution of Y for Dy, as well as for other lanthanoids, causes no notable deviations in the crystallographic values, such as unit-cell parameters and interatomic distances, from those of pure YF (sub 3) .


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 79
Serial Issue: 3
Title: Waimirite-(Y), orthorhombic YF (sub 3) , a new mineral from the Pitinga Mine, Presidente Figueiredo, Amazonas, Brazil and from Jabal Tawlah, Saudi Arabia; description and crystal structure
Affiliation: Universidade de Sao Paulo, Instituto de Geociencias, Sao Paulo, Brazil
Pages: 767-780
Published: 201506
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 33
Accession Number: 2016-007024
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
S00°44'43" - S00°44'43", W60°07'40" - W60°07'40"
Secondary Affiliation: Universidade Federal do Rio Grande do Sul, BRA, BrazilNational Institute of Advanced Industrial Science and Technology, JPN, JapanNational Museum of Nature and Science, JPN, JapanUniversity of Arizona, USA, United StatesRussian Academy of Sciences, RUS, Russian Federation
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201604
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