Eos, Vol. 69, No. 46, November 15, 1988 Rooks Electron Diffraction and High-Resolution Electron Microscopy of Mineral Structures PAGE 1574 Victor A. Drits, Springer-Verlag, New York, xii + 304 pp., 1987 Reviewed by Gordon L. Nord, Jr. This book is a well-written English transla- tion of the original 1981 Russian edition, Strukturnoye issledovaniye mineralov metodami mikrodifraktsii i elecktronnoi mikroskopii vysokogo razresheniya. The 1987 English version has been extensively updated and includes refer- ences up to 1986. The book is essentially a text on the theoretical and experimental as- pects of transmission electron microscopy and has chapters on the reciprocal lattice, electron diffraction (both kinematic and dynamic), and high-resolution electron microscopy. Electron diffraction is emphasized, especial- ly its use for structure analysis of poorly crys- talline and fine-grained phases not readily determined by the more exact X ray diffrac- tion method. Two methods of electron dif- fraction are discussed: selected area electron diffraction (SAED) and oblique-texture elec- tron diffraction (OTED); the latter technique is rarely used in the west and is never dis- cussed in western electron microscopy texts. A SAED pattern is formed by isolating a small micrometer-size area with an aperture and obtaining single-crystal patterns from the diffracted beams. By tilting the sample and obtaining many patterns, a complete picture Meetings Chapman Conference on Sediment Transport Processes in Estuaries PAGE 1579 During the week of June 13-17, 1988, 72 sediment transport researchers "aggregated" at the Universidad Nacional del Sur in Bahia Blanca, Argentina, to participate in an AGU Chapman Conference on Sediment Trans- port Processes in Estuaries. The main goals of the meeting were to discuss recent ad- vances in estuarine science, to appraise prom- ising future research directions, and to devel- op contacts and establish working relation- ships between Latin American and non-Latin- American estuarine researchers. The meeting drew participants from Argentina, Brazil, Chile, Uruguay, Venezuela, the U.S., Canada, of the reciprocal lattice can be taken. An OTED pattern is formed when the incident electron beam passes through an inclined preparation consisting of a great number of thin platy crystals lying normal to the texture axis (axis normal to the support grid). To form an OTED pattern, the plates must all lie on a common face, such as a basal plane in phyllosilicates. Upon tilting the plates, an el- liptical powder diffraction pattern is formed. Intensities measured from these patterns are used for a structural analysis of the platy minerals. Soviet electron microscopists are strong be- lievers in the use of electron diffraction for structure analysis. The advantage of using electron diffraction is the increased spatial resolution obtained in the electron micro- scope, which is especially important in under- standing the structure of mixed-layer or very fine-grained minerals. However, the serious disadvantage of using electron diffraction rel- ative to X ray diffraction is the dependence of the intensity of the diffracted electron beam on the thickness of the sample and on the orientation of the crystal with respect to the incident beam. With increasing thickness, electron diffraction changes from kinematic to dynamic, and the relation between the structure amplitudes and the intensities of the diffracted electron beams, as measured on the photographic plates, becomes ambigu- ous. Only for a limited thickness range will the diffracted intensities correspond to struc- ture amplitudes; usually, thicknesses of 2-5 nm are required. Drits discusses the advantages and disad- vantages of using electron diffraction to solve structures of platy minerals and gives many examples from the Soviet literature. The ap- plication of the OTED method to structure Britain, France, the Federal Republic of Ger- many, The Netherlands, and South Africa. Meeting cosponsors were UNESCO, Secre- taria de Ciencia y Tecnica, Consejo Nacional de Investigaciones Cientificas y Tecnicas, Co- mision de Investigaciones Cientificas de la Provincia de Buenos Aires, Universidad del Sur, Municipalidad de Bahia Blanca, Asocia- cion Argentina de Geofisicos y Geodestas (AGU sister organization), and the Instituto Argentino de Oceanografia (IADO). The conference was organized into seven sessions. The first six consisted of an invited review talk, four to six oral presentations, and a discussion/debate of up to 1 V2 hours in length moderated by the invited speaker. The themes and the invited speakers for each of those sessions were: estuarine bedforms, Jon C. Boothroyd; instrumentation and data anal- yses, Richard W.Sternberg; applications of sediment transport, Henry Bokuniewicz; co- hesive sediments, Ashish J. Mehta; mathe- matical models, Y. Peter Sheng; and inhomo- geneities, John C. Ludwick. Poster papers in these categories were also available through- out the meeting. The seventh session was or- refinements of 2M r muscovite, lM-celadon- ite, lM-phengite, and dioctahedral smectites is described. Application of the SAED meth- od to structural refinements of mixed-layer minerals such as tochilinite and vallerite (both mixed-layer copper-iron-sulfur brucite miner- als) and asbolanes (hybrid mixed-layer man- ganese minerals containing cobalt and nickel is also summarized. Later chapters discuss the use of electron diffraction to study order-dis- order and structural modulations in phyllosi- licates. The final chapter reviews the role of electron diffraction and high-resolution elec- ton microscopy in the discovery of multiple- chain and mixed-chain silicates. Surprisingly, no mention is made of con- vergent beam electron diffraction (CBED). CBED uses a highly convergent beam focused onto a small (<50 nm) area of the sample. In- formation obtained from the patterns can be used to determine the point group and space group of a crystalline material and to deter- mine polytypes in platy minerals. Its absence probably reflects the fact that modern micrs- copes having a low contamination rate are necessary to form convergent beam patterns. These instruments are rare in the Soviet Union. Despite obvious omissions, the book illus- trates the methods of electron diffraction em- ployed by Soviet mineralogists to solve some of the most difficult problems encountered in fine-grained mixed-layer minerals. It there- fore should appeal to mineralogist utlizing electron diffraction and to those attempting to understand the structure of these complex mineral phases. Gordon L. Nord, Jr., is with the U.S. Geological Survey, Reston, Va. ganized around the theme "Future develop- ment of sediment transport research in estu- aries." This session began with the invited talk of Keith Dyer. A discussion featuring all of the invited speakers but enthusiastically joined by meeting participants and lasting several hours ensued. The open discussion periods following the presented papers of each session prove to be valuable in promot- ing the exchanges of ideas and biases among the participants. Many of the papers present- ed have been submitted to the Journal of Geo- physical Research for publication as a confer- ence collection. Several recurrent topics occurred in the presentations and discussions that present new challenges to the research community. A major discussion subject was low-cost method- ologies for sediment transport studies in estu- aries. This is important not only to Latin American researchers typically working with small operational budgets but also to others in the sediment transport community inter- ested in assessing the degree of inhomogen- eity over the extent of the estuary or over even smaller spatial length scales. In the lat- This page may be freely copied.