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Mineralogical ClassificationIMA 2013-071 = zvyaginite

7th Jul 2014 10:33 UTCMarco E. Ciriotti Manager

Reference:

▪ Pekov, I.V., Lykova, I.S., Chukanov, N.V., Yapaskurt, V.O., Belakovskiy, D.I., Zolotarev, A.A., Jr., Zubkova, N.V. (2014): Zvyaginite NaZnNb2Ti2O(OH,F)3(H2O) 4+x(х<1) a new mineral of epistolite group from Lovozero alkaline massif (Kola Peninsula, Russia). Zapiski RMO, 143, 45-63.

Abstract:

A new mineral zvyaginite, epistolite-group member, is found at Mt. Malyi Punkaruaiv, Lovozero alkaline complex, Kola Peninsula, Russia. It occurs in a hydrothermally altered peralkaline pegmatite and is associated with ussingite, microcline, aegirine, sphalerite, vigrishinite, sauconite, etc. Zvyaginite forms rectangular or irregularly shaped lamellae up to 0.1X1 x2 cm flattened on <001>. The mineral is translucent to transparent and colourless, pearly-white, yellowish-brownish, pale pink or lilac- pink. The lustre is nacreous on crystal faces and greasy on broken surface. Mohs' hardness is 21/2—3. Zvyaginite is brittle. Cleavage is {001} perfect. Dmeas = 2.88(3), Dcalc = 2.94 g/cm3. The mineral is optically biaxial (-), alpha = 1.626(5), beta - 1.714(3), gamma = 1.740(5), 2Vmeas - 45(15)°, 2Vcalc = 55°. IR spectrum is given. Chemical composition (wt %; averaged data of 5 electron-microprobe analyses, H20 — by modified Penfield method) is: Na2O 4.74, K2O 0.22, CaO 0.77, MnO 1.36, FeO 0.24, ZnO 9.61, Al2O3 0.19, SiO2 29.42, TiO2 12.33, Nb2O5 27.22, F 1.94, H2O 12.65, -O = F2 -0.82, total 99.87.

The empirical formula calculated on the basis of Si+Al = 4 is: Na1.24K0.04Ca0.11Mn0.16Fe0.03Zn0.96Nb1.66Ti125(Si3.97Al0.03)tot4O15.07(OH)2.10F0.83(H20)4.64. The simplified formula is: NaZnNb2Ti20(OH,F)3(H20)4 + ^ (x < 1). Zvyaginite is triclinic, P-1, a = 8.975(3), b = 8.979(3), c = 12.135(4) A, alpha = 74.328(9)°, beta = 80.651(8)°, gamma 73.959(8)°, V = 900.8(6) A3, Z = 2. The strongest reflections of the X-ray powder pattern (,А-/<Щ) are: 11.72-100<001>; 5.83-40<002>; 5.28-53<-l-ll, 112>; 4.289-86<200, 021>; 3.896-36<-l-12, -201, 003, 022, 113>, 2.916-57<310, 132, 004>, 2.862-72<130, 312>. The crystal structure model was obtained on a single crystal, R = 0.159. Zvyaginite and epistolite are close in the structure of the NbTiSiO motif but different from one another in composition of the О layer in the HOH block. Zvyaginite is named in honor of Russian crystallographer, crystal chemist and physicist Boris B. Zvyagin (1921-2002). The type specimen is deposited in the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow.

26th Jul 2014 09:06 UTCKnut Edvard Larsen 🌟 Manager

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