Titre du document / Document title
Labyrinthite (Na, K, Sr)35Ca12Fe3Zr6TiSi51O144(O, OH, H2O)9Cl3, a new mineral with a modular eudialyte-like structure from Khibiny Alkaline Massif, Kola Peninsula, Russia
Auteur(s) / Author(s)KHOMYAKOV A. P.
NECHELYUSTOV G. N.
RASTSVETAEVA R. K.
Résumé / Abstract
Labyrinthite was found on the Nyorkpakhk Mt (Khibiny massif), occurring in hyperagpaitic pegmatite as anhedral rounded grains 0.5-1 cm in cross-size. It associates with potassium feldspar, sodalite, alkaline amphibole, aegirine, pectolite, lamprophyllite, lomonosovite, villiaumite, etc. At the surface, grains of the mineral are replaced by aggregates of zirsinalite, lovozerite and thermonatrite; Color bright pink, streak white, transparent, luster vitreous; brittle, with conchoidal fracture. Mohs' hardness 5-6. D(meas.) =2.88(2) g/cm3
(volumetric method) D(calc.) = 2.87 g/cm3
Optically uniaxial, positive, n0
= 1.597(1), ne
= 1.601(1). Trigonal, space group R3, a = 14.239(1), c = 60.733(7) Å, V= 10664(3) Å. Z= 3. The strongest lines of the powder diffraction pattern [d, Å (I)(hkl)] are: 2.977(100)(1.3.10), 2.853(88)(048), 4.324(68)(0.2.10), 3.230(44)(0.2.16), 3.550(39)(220), 2.685(38)(140), 3.049(36)(1.1.18), 2.605(36)(0.3.18), 5.70(34)(024), 3.173(34)(1.2.14). The IR data are given. Chemical composition (wt%, electron probe, H2
O content by the Penfield method): Na2
O 16.77, K2
O 1.11, CaO 10.73, SrO 1.24, FeO 2.56, MnO 1.00, Ce2
0.67, Cl 1.70, F 011, H2
O 1.58, -O=(Cl,F)2
0.43, total 99.25. Empirical formula (based on total of cations Si +Zr+ Ti = 57.7 as determined by crystal structure analysis) is (Na33.30
O. Simplified formula: (Na,K,Sr)35
. The mineral is named labyrinthite (from the Greek 'labyrinthos' [labyrinth]) for its unusually complex crystal structure, whose unit cell contains about 800 cations and anions distributed over more than 100 crystallographic sites. The crystal structure is characterized by the presence of two types of modules (alluaivite-like and eudialyte-like) alternating along the triad axis, causing labyrinthite to have a double c period of its unit cell relatively to eudialyte, and a close crystal chemical relationship to rastsvetacvite (ZRMO, 2006, No. 1). According to the authors' crystal chemical systematics of the eudialyte group, the mineral belongs to one of its three principal subgroups characterized by the 24-layered structural array. Labyrinthite is a late-pegmatitic mineral formed during the final stages of hyperagpaitic pegmatite formation. Type material is deposited at the Fersman Mineralogical Museum Moscow.
Revue / Journal TitleZapiski Vserossijskogo mineralogičeskogo obŝestva
Source / Source
2006, vol. 135, no
2, pp. 38-49 [12 page(s) (article)]
Langue / Language
Editeur / Publisher
Nauka, Sankt-Peterburg, RUSSIE, FEDERATION DE
Localisation / Location
INIST-CNRS, Cote INIST : 4673, 35400014675517.0030
Nº notice refdoc (ud4) : 18813948