Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by PEKOV, I. V. Articles by CHISTYAKOVA, N. I. Search for Related Content GeoRef GeoRef Citation

Sphaerobertrandite, Be₃SiO₄(OH)₂

¹ Faculty of Geology, Moscow State University, Vorobievy Gory, 119899 Moscow, Russia
² Institute of Chemical Physics Problems, 142432 Chernogolovka, Moscow Oblast, Russia
³ Norsk Hydro ASA, Research Centre Porsgrunn, P. O. Box 2560, N-3907 Porsgrunn, Norway
⁴ Department of Earth Sciences, University of Pisa, v. S. Maria 53, I-56126 Pisa, Italy
⁵ Department of Mineralogy and Petrology, University of Torino, Via Valperga Caluso 35, I-10125 Torino, Italy
⁶ NPO Regenerator, Skladochnaya ul. 6, 127018 Moscow, Russia
⁷ Department of Physics, University of Oslo, P.O. Box 1032 Blindern, N-0315 Oslo, Norway
⁸ All-Russian Institute of Mineral Resources, Staromonetnyi per. 31, 109017 Moscow, Russia

^* Corresponding author, e-mail: igorpekov{at}mtu-net.ru

The insufficiently studied beryllium silicate sphaerobertrandite has been known since 1957. The present work presents new findings, verifies that the mineral is a valid species with a unique structure. The original name sphaerobertrandite has been kept in spite of its unjustifiable connection to bertrandite. The mineral is named after the typical spherulitic morphology of its aggregates, and its similarity to bertrandite in the main chemical constituents. Sphaerobertrandite was recently found in alkaline pegmatites at Sengischorr Mountain, Lovozero massif, Kola peninsula, Russia, inside epididymite segregations, coexisting with eudidymite, aegirine, mangan-neptunite, etc., and in Tuften quarry, Tvedalen, South Norway, coexisting with hambergite, analcime, chiavennite, etc. The mineral forms spherulites up to 2 mm, as well as fibrous crusts. Sphaerobertrandite from Sengischorr Mountain occurs as thin tabular, prismatic crystals up to 0.5 x 0.2 x 0.05 mm in aggregates overgrowing epididymite. The main crystal form is {001}, small faces {012}, {102} and {10–2} are present. Transparent to translucent; colourless, white, yellow, brownish, greyish, beige. Streak white. Lustre vitreous. Mohs' hardness 5. Brittle. Cleavage perfect on (001). D (meas.) is 2.46 - 2.54, D (calc.) is 2.52 g/cm³. Biaxial, negative, = 1.597(3), β = 1.607(4), = 1.616(3), 2V (meas) is 70(±20)° Orientation: Z = c. IR spectrum is unique; frequencies of absorption bands are (cm^–1; sh — shoulder, w — weak; the most intensive bands are underlined): 3605, 3540, 3505, 3370sh, 3250sh, 3060w, 1620sh, 1400sh, 1150, 1115, 1090sh, 995sh, 933, 900, 835, 768, 721, 680sh, 639, 612, 573w, 555w, 491, 424, 410sh. Chemical composition of the sample from Sengischorr Mountain is: BeO 45.88, SiO₂ 38.46, H₂O+ 12.54, total 96.88 wt. %, corresponding to Be_2.97Si_1.03O_4.06(OH)_1.94· 0.155H₂O. Monoclinic, P2₁/c, with a = 5.081(3), b = 4.639(1), c = 17.664(9) Å, β= 106.09(5)°, V = 400.0 ų, with a strongly pseudo-orthorhombic cell, which is the likely reason for the samples being invariably twinned by pseudo-merohedry. The strongest lines in the X-ray powder pattern are (d in Å -I[hkl]): 4.885–90[100]; 4.236–62[004]; 3.161–100[111, 11–3]; 2.836–70[104]; 2.538–55[20–2]; 2.318–90[020]; 2.174–55[10–8]. The crystal structure has been refined to R = 0.090. Better refinement could not be achieved because of twinning by pseudo-merohedry with low obliquity, which produces partial overlapping of reflections. The structure consists of mixed framework formed by Be- and Si-tetrahedra which comprises 6- and 4- membered rings. All vertices of SiO₄ tetrahedra are shared with 2 BeO₄ tetrahedra. The OH anions are shared only between two Be tetrahedra. The structure contains Be(3)O₃ chains screwed around 2₁ axis and reinforced by SiO₄ tetrahedra. These (Be, Si, O) chains are linked by the dimers Be(2)₂O₆ and by Be(1)O₄ tetrahedra.

Key-words: sphaerobertrandite, beryllium silicate, crystal structure, alkaline rocks, Lovozero, Kola peninsula, Tvedalen, Norway.

This article has been cited by other articles:

				A. G. Christy A Monte Carlo study of short- and long-range order of tetrahedral cations in sapphirine and khmaralite American Mineralogist, February 1, 2009; 94(2-3): 270 - 282. [Abstract] [Full Text] [PDF]

				I. V. Pekov, N. V. Zubkova, N. V. Chukanov, A. A. Agakhanov, D. I. Belakovskiy, L. Horvath, Y. E. Filinchuk, E. R. Gobechiya, D. Yu. Pushcharovsky, and M. Kh. Rabadanov NIVEOLANITE, THE FIRST NATURAL BERYLLIUM CARBONATE, A NEW MINERAL SPECIES FROM MONT SAINT-HILAIRE, QUEBEC, CANADA Can Mineral, October 1, 2008; 46(5): 1343 - 1354. [Abstract] [Full Text] [PDF]

				J. L. Jambor, J. L. Jambor, and A. C. Roberts New Mineral Names American Mineralogist, November 1, 2003; 88(11-12): 1836 - 1840. [Full Text] [PDF]

				R. F. Martin ENCYCLOPEDIA OF MINERAL NAMES: THIRD UPDATE Can Mineral, August 1, 2003; 41(4): 1075 - 1096. [Full Text] [PDF]