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Fluorcalciobritholite, (Ca,REE) (sub 5) [(Si,P)O (sub 4) ] (sub 3) F, a new mineral; description and crystal chemistry

Igor V. Pekov, Marco Pasero, Asiya N. Yaskovskaya, Nikita V. Chukanov, Dmitry Yu. Pushcharovsky, Stefano Merlino, Natalia V. Zubkova, Natalia N. Kononkova, Yury P. Men'shikov and Aleksandr E. Zadov
Fluorcalciobritholite, (Ca,REE) (sub 5) [(Si,P)O (sub 4) ] (sub 3) F, a new mineral; description and crystal chemistry
European Journal of Mineralogy (February 2007) 19 (1): 95-103

Abstract

The new mineral fluorcalciobritholite, ideally Ca (sub 3) Ce (sub 2) (SiO (sub 4) ) (sub 2) (PO (sub 4) )F, has been found at Mount Kukisvumchorr, Khibiny alkaline complex, Kola Peninsula, Russia, in veinlets which contains aggregates of orthoclase, nepheline, sodalite and biotite in association with grains of fayalite, gadolinite-(Ce), zircon, monazite-(Ce), zirconolite ("polymignite"), fluorapatite, fluorite, molybdenite, lollingite and graphite. Fluorcalciobritholite forms long-prismatic hexagonal crystals up to 0.5X10 mm; the main crystal form is the hexagonal prism {10-10}. The mineral is transparent, with a pale pinkish to brown colour and a white streak. The hardness (Mohs) is 5.5, and the observed density is 4.2(1) g/cm (super 3) . Optically, it is uniaxial (-) with w 1.735(5), epsilon 1.730(5). Electron microprobe gave the following empirical formula based on [Si+P+S] = 3 apfu: [Ca (sub 2.80) (Ce (sub 0.93) La (sub 0.54) Nd (sub 0.26) Y (sub 0.18) Pr (sub 0.08) Sm (sub 0.03) Gd (sub 0.03) Dy (sub 0.02) Yb (sub 0.02) Er (sub 0.01) ) (sub Sigma 2.12) Th (sub 0.04) Mn (sub 0.03) Sr (sub 0.02) ] (sub Sigma 4.99) [(Si (sub 1.94) P (sub 1.06) ) (sub Sigma 3) O (sub 12) ] [F (sub 0.76) O (sub 0.22) Cl (sub 0.01) ] (sub Sigma 0.99) (Z = 2). The IR spectrum of metamict fluorcalciobritholite from Siberia showed a marked similarity with those of hydroxylbritholite-(Ce) and hydroxylbritholite-(Y). The strongest lines of the X-ray powder pattern [d in Aa (I) (hkl)] are: 3.51 (45) 002, 3.15 (70) 102, 2.85 (100) 211, 121, 2.78 (60) 300. The mineral is hexagonal, space group P6 (sub 3) /m, with a = 9.580(7), c = 6.985(4) Aa, V = 555.2(7) Aa (super 3) . The crystal structure was refined from single-crystal X-ray diffraction data to R (sub F) = 0.029. Fluorcalciobritholite, whose simplified formula is (Ca,REE) (sub 5) [(Si,P)O (sub 4) ] (sub 3) F, differs from fluorbritholite in having Ca$GTSigma REE, and differs from fluorapatite in having Si$GTP. Its compositional field falls within the limits Ca (sub 2.5) REE (sub 2.5) (SiO (sub 4) ) (sub 2.5) (PO (sub 4) ) (sub 0.5) F (boundary with fluorbritholite) and Ca (sub 3.5) REE (sub 1.5) (SiO (sub 4) ) (sub 1.5) (PO (sub 4) ) (sub 1.5) F (boundary with fluorapatite). Both the mineral and its name have been approved by the IMA Commission on New Minerals and Mineral Names.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 19
Serial Issue: 1
Title: Fluorcalciobritholite, (Ca,REE) (sub 5) [(Si,P)O (sub 4) ] (sub 3) F, a new mineral; description and crystal chemistry
Affiliation: Moscow State University, Faculty of Geology, Moscow, Russian Federation
Pages: 95-103
Published: 200702
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 36
Accession Number: 2007-084269
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
N35°00'00" - N71°00'00", W25°00'00" - E75°00'00"
N67°00'00" - N68°00'00", E33°00'00" - E34°00'00"
N66°00'00" - N70°00'00", E32°00'00" - E42°00'00"
N37°00'00" - N83°00'00", W170°00'00" - E28°00'00"
Secondary Affiliation: Universita di Pisa, ITA, ItalyFersman Mineralogical Museum, RUS, Russian FederationInstitute of Problems of Chemical Physics, RUS, Russian FederationInstitute of Geochemistry and Analytical Chemistry, RUS, Russian FederationGeological Institute of Kola Science Centre, RUS, Russian FederationNPO Regenerator, RUS, Russian Federation
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200739
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