American

Mineralogist

1996, Volume 81, May-June, number 5-6

PRESIDENTIAL ADDRESS

J.J. Papike

Pyroxene as a recorder of cumulate formational processes in asteroids, Moon, Mars, Earth: Reading the record with the ion microprobe 525

LETTERS

Frank C. Hawthorne, Giancarlo Della Ventura, and Jean-Louis Robert

Short-range order of (Na,K) and Al in tremolite: An infrared study 781

Anatoly B. Belonoshko, Leonid S. Dubrovinsky, and Natalya A. Dubrovinsky

A new high-pressure silica phase obtained by molecular dynamics 785

ARTICLES

Björn Winkler, Peter Blaha, and Karlheinz Schwarz

Ab initio calculation of electric-field--gradient tensors of forsterite 545

Simon J. Kitchin, Simon C. Kohn, Ray Dupree, C. Michael B. Henderson, and Kuniaki Kihara

In situ ²⁹Si MAS NMR studies of structural phase transitions of tridymite 550

Michael A. Carpenter and Daniela Cellai

Microstructures and high-temperature phase transitions in kalsilite 561

Bruno Reynard, Fouzia Takir, Fran�ois Guyot, Gabriel D. Gwanmesia, Robert C. Liebermann, and Philippe Gillet

High-temperature Raman spectroscopic and X-ray diffraction study of -Mg₂SiO₄: Insights into its high-temperature thermodynamic properties and the - to -phase-transformation mechanism and kinetics 585

Lee A. Groat, Stefan Kek, Ulrich Bismayer, Claudia Schmidt, Hans Georg Krane, Hinrich Meyer, Leona Nistor, and Gustaaf Van Tendeloo

A synchrotron radiation, HRTEM, X-ray powder diffraction, and Raman spectroscopic study of malayaite, CaSnSiO₅ 595

G. Artioli, A. Pavese, M. Bellotto, S.P. Collins, and G. Lucchetti

Mn crystal chemistry in pumpellyite: A resonant scattering powder diffraction Rietveld study using synchrotron radiation 603

Isabelle Martinez, Jianzhong Zhang, and Richard J. Reeder

In situ X-ray diffraction of aragonite and dolomite at high pressure and high temperature: Evidence for dolomite breakdown to aragonite and magnesite 611

Thomas Armbruster, Ping Yang, and Bernard W. Liebich

Mechanism of the SiO4 for CO₃ substitution in defernite, Ca₆(CO₃)_1.58(Si₂O₇)_0.21(OH)₇[Cl_0.50(OH)_0.08(H₂O)_0.42]: A single-crystal X-ray study at 100 K 625

George E. Harlow

Structure refinement of a natural K-rich diopside: The effect of K on the average structure 632

Rex A. Couture and Robert F. Dymek

A reexamination of absorption and enhancement effects in X-ray fluorescence trace element analysis 639

Philippe Gillet, Jean-Marie MalŽzieux, and Jean-Paul Itiè

Phase changes and amorphization of zeolites at high pressures: The case of scolecite and mesolite 651

Irina Kiseleva, Alexandra Navrotsky, Igor A. Belitsky, and Boris A. Fursenko

Thermochemistry and phase equilibria in calcium zeolites 658

Irina Kiseleva, Alexandra Navrotsky, Igor A. Belitsky, and Boris A. Fursenko

Thermochemistry of natural potassium sodium calcium leonhardite and its cation-exchanged forms 668

Judy Baker and T.J.B. Holland

Experimental reversals of chlorite compositions in divariant MgO + Al₂O₃ + SiO₂ + H₂O assemblages 676

J. Longhi and C.M. Bertka

Graphical analysis of pigeonite-augite liquidus equilibria 685

Donna L. Whitney, Trudy A. Mechum, Yildirim Dilek, and Scott M. Kuehner

Modification of garnet by fluid infiltration during regional metamorphism in garnet through sillimanite-zone rocks, Dutchess County, New York 696

Liping Wang, Youxue Zhang, and Eric J. Essene

Diffusion of the hydrous component in pyrope 706

Jonathan Icenhower and David London

Experimental partitioning of Rb, Cs, Sr, and Ba between alkali feldspar and peraluminous melt 719

Paola Bonazzi, Silvio Menchetti, and Thomas Reinecke

Solid solution between piemontite and androsite-(La), a new mineral of the epidote group from Andros Island, Greece 735

Edward S. Grew, Donald R. Peacor, Roland C. Rouse, Martin G. Yates, Shu-Chun Su, and Nicholas Marquez

Hyttsjöite, a new, complex layered plumbosilicate with unique tetrahedral sheets from Långban, Sweden 743

Oded Navon, F.A. Frey, and E. Takazawa

Magma transport and metasomatism in the mantle: A critical review of current geochemical models---Discussion 754

Jane E. Nielson and Howard G. Wilshire

Magma transport and metasomatism in the mantle: A critical review of current geochemical models---Reply to Navon et al. 760

NEW MINERAL NAMES 766

PRESENTATION OF AWARDS FOR 1995

Bernard W. Evans

Presentation of the Roebling Medal of the Mineralogical Society of America for 1995 to William S. Fyfe 771

William S. Fyfe

Acceptance of the Roebling Medal of the Mineralogical Society of America for 1995 773 Read!

Eric J. Essene and James R. O'Neil

Presentation of the Mineralogical Society of America Award for 1995 to Zachary D. Sharp 775

Zachary D. Sharp

Acceptance of the Mineralogical Society of America Award for 1995 777

MEMORIAL

Larry A. Haskin

Memorial of Carl Tolman, 1897--1995 779