The Clay Minerals Society

Clays and Clay Minerals¨

Volume 45 Number 3 June 1997

Contents

Refinement of an Amesite-2H1 Polytype from Postmasburg, South Africa
Hong Zheng and Sturges W. Bailey 301

Interaction of Vermiculite with Aliphatic Amides (Formamide, Acetamide and Propionamide): Formation and Study of Interstratified Phases in the Transformation of Mg- to NH4- Vermiculite
Antonio Ruiz-Conde, Antonio Ruiz-Amil, Jose L. Perez-Rodriguez, Pedro J. Sanchez-Soto and Francisco Aragon de la Cruz 311

Comparison of the Mineralogical and Chemical Composition of 2 Shales from the Western Canada Sedimentary Basin and the United States Gulf Coast
Patrice de Caritat, John Bloch, Ian Hutcheon, Fred J. Longstaffe and Hugh J. Abercrombie 327

Sorption of Atrazine by Al- and Ca-Saturated Smectite
B. L. Sawhney and S. S. Singh 333

The Chemical Composition of Serpentine/Chlorite in the Tuscaloosa Formation, United States Gulf Coast: EDX vs. XRD Determinations, Implications for Mineralogic Reactions and the Origin of Anatase
P. C. Ryan and R. C. Reynolds, Jr. 339

Phosphates in Some Missouri Refractory Clays
Robert B. Hall, Eugene E. Foord, David J. Keller and Walter D. Keller 353

Experimental Study on the Formation of Zeolites from Obsidian by Interaction with NaOH and KOH Solutions at 150 and 200 ° C
Motoharu Kawano and Katsutoshi Tomita 365

Textural Transition and Genetic Relationship between Precursor Stevensite and Sepiolite in Lacustrine Sediments (Jbel Rhassoul, Morocco)
Azeddine Chahi, Bertrand Fritz, Joelle Duplay, Francis Weber and Jacques Lucas 378

Illite-Smectite Alteration and Accompanying Reactions in a Pennsylvanian Underclay Studied by TEM
F. Elsass, J. Srodon and M. Robert 390

Crystallographic Controls on the Alteration of Microcline Perthites from the Spruce Pine District, North Carolina
Julia M. Sheets and Rodney T. Tettenhorst 404

Quantitative Phase Analysis of Bidi-Koum Bauxites (Guinea)
Frank Feret, Monique Authier-Martin and István Sajó 418

Characterization of Iron-Manganese Concretions in Kentucky Alfisols with Perched Water Tables
Min Zhang and A. D. Karathanasis 428

Analytical Electron Microscopic Study of the Noncrystalline Products Formed at Early Weathering Stages of Volcanic Glass
Motoharu Kawano, Katsutoshi Tomita and Yasushi Shinohara 440

Surface Structural Model for Ferrihydrite
A. Manceau and W. P. Gates 448

XRD Measurement of Mean Crystallite Thickness of Illite and Illite/Smectite: Reappraisal of the Kubler Index and the Scherrer Equation
Victor Drits, Jan Srodon and D. D. Eberl 461

Notes

Reduction and Reoxidation of Nontronite: The Data Reassessed
L. Heller-Kallai 476

A Warning on the Use of Mössbauer Spectroscopy in Semiquantitative Analysis of Soils
Celia Saragovi and Ana Mijovilovich 480

Enhanced Second-Order Optical Nonlinearity of Dye Molecules Adsorbed onto Laponite Particles
Carlo Boutton, Martti Kauranen, André Persoons, Michael P. Keung, Katrien Y. Jacobs and Robert A. Schoonheydt 483

The Effect of Chemical Pretreatments on the Composition of Natural Illite
Philip E. Rosenberg and Robert L. Hooper 486