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Titre du document / Document title

Ikranite, (Na, H3O)15(Ca, Mn, REE)6Fe3+2Zr3(□, Zr)(□Si)Si24O66(O, OH)6Cl . nH2O and raslakite Na15Ca3Fe3(Na, Zr)3Zr3(Si, Nb) (Si25O73)(OH, H2O)3(Cl, OH): The new eudialyte-group minerals from Lovozero Massif, Kola Peninsula

Auteur(s) / Author(s)

CHUKANOV N. V. ; PEKOV I. V. ; ZADOV A. E. ; KOROVUSHKIN V. V. ; EKIMENKOVA I. A. ; RASTSVETAEVA R. K. ;

Résumé / Abstract

Ikranite and raslakite were discovered in two peralkaline pegmatites at the Karnasurt Mt of Lovozero alkaline massif, in associations with aegirine, microcline, lorenzenite, nepheline, lamprophyllite, murmanite, arfvedsonite (for ikranite) and with microcline, aegirine, nepheline, lamprophyllite, kazakovite, terskite, fluorcaphite (for raslakite). The new minerals form brownish-yellow (ikranite) or brownish-red (raslakite) grains up to 2-3 cm in size. Brittle, cleavage non-perfect, Mobs' hardness 5. Both are optically positive. Ikranite is often weakly biaxial, raslakite is uniaxial: ω = 1.612 (1) and 1.608; ε = 1.615 and 1.611; Dmeas = 2.82 (3) and 2.95 (1) g/cm3, Dcalc = 2.83 and 2.945 g/cm3, respectively. Both minerals are trigonal, space groups R3m and R3, a = 14.167 (2) and 14.229 (7), c = = 30.081 (2) and c = 30.019 (15) Å; V = 5228.5 and 5263.5 Å3, respectively; for both R = 0.037. Ikranite differs from all other eudialyte-group minerals by the prevailing of vacancies in the sites M (3) and M (4) at the centers of the 9-membered Si-rings and by the strong predominance of [6]Fe3+ over [4]Fe2+ in the M (2) position linking 6-membered Ca-rings. In ikranite Na is partly substituted by H3O; in raslakite M (1) is transformed into two independent sites M (1,1) and M (1,2) occupied mainly by Fe and Ca, respectively. The position M (2) is statistically occupied by [5]Na, [5]Mn and [4]Zr. These structural features are in good agreement with the data of IR and Mössbauer spectroscopic data. The strongest lines of the powder diffraction pattern [d, Å (I, %) (hkl)] are - ikranite: 6.41 (41) (104), 4.30 (91) (205), 3.521 (57) (027), 3.205 (44) (208), 2.963 (92) (315, 13-5), 2.841 (100) (404); raslakite: 4.311 (66) (205), 4.095 (37) (116, 11-6), 3.209 (58) (208), 3.023 (40) (119, 11-9), 2.974 (86) (315, 13-5), 2.853 (100) (404). Chemical compositions of ikranite and raslakite (wt. %, electron probe, H2O content - by thermogravimetric method, for Fe in ikranite - wet analysis) correspond to the empirical formulae (Z = 3): Na7.56(H3O)6.64K0.27Ca3.31 Sr0.46Ce0.27La0.11Mn2+1.41Fe2+0.16Fe3+1.77Zr3.33Ti0.14Hf0.04Nb0.06Si24O72Cl0.74 . 2.6H2O (ikranite); Na16.02K0.32Ca3.13 Sr0.21Mg0.22 Fe2.17Mn0.88Ce0.16La0.08 Ti0.14Zr3.80 Hf0.06Nb0.17Al0.16Si25.40Cl1.18 H4.66O76.465 (raslakite). The minerals were named for Russian akronym IKRAN (Institut Kristallografii Rossiiskoy Adademii Nauky) and from Raslak Cirques near Kedykverpakhk Mt. Their type materials are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Revue / Journal Title

Zapiski Vserossijskogo mineralogičeskogo obŝestva    ISSN  0869-6055 

Source / Source

2003, vol. 132, no5, pp. 22-33 [12 page(s) (article)]

Langue / Language

Russe

Editeur / Publisher

Nauka, Sankt-Peterburg, RUSSIE, FEDERATION DE  (1992) (Revue)

Localisation / Location

INIST-CNRS, Cote INIST : 4673, 35400011463735.0020

Nº notice refdoc (ud4) : 15861096



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