Titre du document / Document title

Alsakharovite-Zn, NaSrKZn(Ti, Nb)⁴(Si⁴O¹²]²(O, OH)⁴.7H²O, a new mineral of the labuntsovite group from Lovozero Massif, Kola peninsula

Auteur(s) / Author(s)

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

Résumé / Abstract

Alsakharovite-Zn, a new mineral of the labuntsovite group, was found in cavities of eudialyte-aegirine-feldspar pegmatite at Lepkhe-Nelm Mt, Lovozero alkaline massif (Kola peninsula, Russia). It is a hydrothermal mineral associated with lamprophyllite, natrolite, halloysite, rancieite, kuzmenkoite-Zn, tsepinite-Na, vinogradovite, etc. It occurs as coarse flattened-prismatic crystals up to 8 x 2 x 0.5 mm in size. Translucent to transparent; white, pale brown, colorless. Streak white, luster vitreous. Brittle, cleavage not observed, fracture uneven. Mohs' hardness ∼5. D^meas 2.90, D^calc 2.93 g/cm₃. Optically biaxial (+), a 1.680, β 1.687, γ 1.785, 2V (meas) 25 (10)°. Chemical composition (electron probe, H²O by TGA), wt.%: Na²O 2.04, K²O 2.43, CaO 1.48, SrO 4.49, BaO 3.65, MgO 0.04, MnO 0.11, FeO 0.22, ZnO 5.02, Al²O³ 0.15, SiO² 39.23, TiO² 18.89, Nb²O⁵ 12.57, H²O 11.1; Total 101.42. The empirical formula calculated on (Si,Al)⁸O²⁴(O,OH)⁸ is: Na0^.68Ca⁰.³²)^Σ1.00(Sr^0.53Na^0.12)^Σ0.65(K^0.63Ba^0.29)^Σ0.92 (Zn^0.75Fe^0.04Mn^0.02Mg^0.01)^Σ0.82(Ti^2.88Nb^1.15)Σ^4.03(Si^7.96Al^0.04)^Σ8O²⁴[O^2.58(OH)^1.42]^Σ4.6.80H²O. Simplified formula - NaSrKZn(Ti,Nb)⁴[Si⁴O¹²]²(b,OH)4.7H²O (Z = 2). Crystal structure was studied, R = 0.058. Monoclinic, Cm. Observed microtwinning on planes (001) and (-401). Unit cell dimensions: a = 14.495 (10), b = 13.945 (10), c = 7.838(8) Å, β = 117.75(7)°, V = 1402(3) Å₃. Representative of the gutkovaite structural type. Newly for labuntsovite-group minerals, cation site A2 was found; mainly occupied by Sr. The strongest lines of X-ray powder pattern (d, Å - I[hkl]) are: 6.96-7[020, 001]; 3.22-80[402, 421, 400]; 3.11-90[041, 022, 240]; 2.60-35[151, 241, 202], 2.50-40[441, 403], 1.74-30[080, 004], 1.70-40[463, 444, 461, 442]. IR spectrum is given. Alsakharovite-Zn is named in the memory of Russian geologist Aleksey S. Sakharov (1910-1996) who studied Lovozero massif, with consideration of Zn prevailing in D-site. Type specimen is deposited in Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Revue / Journal Title

Zapiski Vserossijskogo mineralogičeskogo obŝestva   ISSN 0869-6055 

Source / Source

2003, vol. 132, n^o1, pp. 52-58 [7 page(s) (article)]

Langue / Language

Russe

Editeur / Publisher

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

Localisation / Location

INIST-CNRS, Cote INIST : 4673, 35400011679348.0050