|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia
2 Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
3 Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
4 Department of Geological Sciences, University of Maine, 5790 Bryand Research Center, Orono, Maine 04469-5790, U.S.A.
Beryllian sapphirine Mg4–xAl4+x[Al4+x–2yBeySi2–x+yO18]O2 has been synthesized from starting compositions with y 
1 at x = 0 and y 0.5 at x = 0.5, P = 0.1–1.3 GPa, T = 700–1350 °C. Electron diffraction shows the sapphirines are dominantly the 1A polytype but lamellae of a 2M phase are consistently present. This is the first 2M sapphirine synthesized in the laboratory, and the first known to be devoid of Fe2+. No superstructure reflections corresponding to the doubled tetrahedral chain repeat of khmaralite were observed, probably due to insufficient annealing time. Cell parameters of the synthetic sapphirine decreased strongly and linearly with Be content (2.7 vol% decrease from y = 0 to y = 1). In agreement with crystal-chemical considerations, experiments with starting compositions of y > 1.0 resulted in additional crystalline phases either coexisting with the limiting sapphirine (y = 1) or without it. At 900 °C, 1.3–2.0 GPa, the saturating assemblage is surinamite + chrysoberyl + forsterite, which is chemically equivalent to sapphirine with y = 1.5. The current lack of natural khmaralite with Be > 0.78 cations per formula unit (pfu) is likely due to the bulk composition of the host rocks being too rich in SiO2 and Al2O3 for forsterite to be stable. Addition of BeO to the MgO-Al2O3-SiO2 system evidently enlarges the stability field of sapphirine + forsterite relative to its restricted range in the BeO-free system.
This article has been cited by other articles:
|
|
 |
|
  E. S. Grew, J. Barbier, J. Britten, U. Halenius, and C. K. Shearer The crystal chemistry of welshite, a non-centrosymmetric (P1) aenigmatite-sapphirine-surinamite group mineral American Mineralogist, January 1, 2007; 92(1): 80 - 90. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. S. GREW, M. G. YATES, C. K. SHEARER, J. J. HAGERTY, J. W. SHERATON, and M. SANDIFORD Beryllium and Other Trace Elements in Paragneisses and Anatectic Veins of the Ultrahigh-Temperature Napier Complex, Enderby Land, East Antarctica: the Role of Sapphirine J. Petrology, May 1, 2006; 47(5): 859 - 882. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. G. Christy and K. Gatedal Extremely Pb-rich rock-forming silicates including a beryllian scapolite and associated minerals in a skarn from Langban, Varmland, Sweden Mineralogical Magazine, December 1, 2005; 69(6): 995 - 1018. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. S. Grew, J. Barbier, J. Britten, M. G. Yates, V. O. Polyakov, E. P. Shcherbakova, U. Halenius, and C. K. Shearer Makarochkinite, Ca2Fe42+Fe3+TiSi4BeAlO20, a new beryllosilicate member of the aenigmatite-sapphirine-surinamite group from the Il'men Mountains (southern Urals), Russia American Mineralogist, August 1, 2005; 90(8-9): 1402 - 1412. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. G. Christy, A.G. Christy, and E.S. Grew Synthesis of beryllian sapphirine in the system MgO-BeO-Al2O3-SiO2-H2O and comparison with naturally occurring beryllian sapphirine and khmaralite, Part 2: A chemographic study of Be content as a function of P, T, assemblage and FeMg-1 exchange American Mineralogist, February 1, 2004; 89(2-3): 327 - 338. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
