Plan of Review This review of clay microstructure is aimed at the
diverse group of professionals who share an interest in the properties
of fine-grained minerals in sediments. During the last several decades,
members of this group have included geologists, soil scientists, soil
engineers, engineering geologists, and ceramics scientists. More
recently, it has included significant numbers of marine geologists and
other engineers. Each of the disciplines has developed special
techniques for investigating properties of clay sediments that have
proven to be fruitful in answering questions of central interest.
Knowledge of clay microstructure-the fabric of a sediment and the
physico- chemical interactions between its components-is fundamental to
all these disciplines (Mitchell 1956; Lambe 1958a; Foster and De 1971).
Clay fabric refers to the spatial distribution, orientations, and
particle-to-particle relations of the solid particles (generally those
less than 3. 9 /Lm in size) of sediment. Physico-chemical interac- tions
are expressions of the forces between the particles. In this review, we
trace the historical development of under- standing clay microstructure
by discussing key scientific papers published before 1986 on
physico-chemical interactions in fine- grained sediments and on clay
fabric. Since the development follows an intricate path, the current
view of clay microstructure is summarized. This summary includes a
discussion of the present state of knowledge, the observations made so
far, and the facts that are now established.