The papers in this edition of the MRS BULLETIN were among those presented during a workshop entitled “SAS Interfaces '87: Microscopy for the Archaeologist.” The workshop was sponsored by the Society for Archaeological Sciences at the 52nd annual meeting of the Society for American Archaeology held in Toronto, Ontario, May 1987. The Society for Archaeological Sciences is an interdisciplinary professional society for researchers involved in the broad spectrum of physical science applications to archaeology in order to promote interaction among scientists interested in different aspects of common research problems.

Archaeometry, i.e., “archaeological science,” is concerned with the physical analysis of archaeological materials and the application of techniques from the laboratory sciences to the objectives and needs of archaeology. It includes such activities as compositional analysis, reconstruction of past technologies and processes, remote sensing, paleo-environmental reconstruction, and of course, isotopic and other chronometric dating methods. Such techniques alone, however, yield results that mean little without appropriate application to anthropological problems. The chief concern of archaeologists is to choose the most appropriate analysis method to achieve results that are useful in interpreting cultural behavior. To that end, laboratory analysts need to be aware of the interests and concerns of archaeologists, and archaeologists need to be able to understand the technical advances in archaeometry to incorporate them into their research.

Petrographic analysis is not new to the study of archaeological ceramics, but it is receiving more attention as it is applied to interesting and diverse archaeological problems. Petrography was developed by geologists to identify minerals in rocks. Archaeologists use it to study the minerals that occur in prehistoric clay matrices transformed by heat to a rocklike state.

Petrographic analysis requires a polarizing microscope and a piece of ceramic, called a thin section, 30 microns (0.03 mm) thick. As light from this specialized microscope passes through a mineral, it produces optical properties unique to that mineral. Birefringence and pleochroism are two such properties used to identify minerals, while physical properties such as cleavage and relief are also important discriminators. Several references fully explain these properties and relate them to specific minerals and rocks.

Using petrographic techniques, as many as five materials can be studied in a ceramic—the clay itself, natural inclusions in the clay, purposefully added inclusions, and glazes or slips on the clay surface. Under certain conditions the clay or inclusions may melt and a fifth material, glass, may form. Depending on the research problem to be addressed and the samples available, the petrdgrapher studies one or more of these materials.

Metallography is undoubtedly one of the most useful techniques for addressing the numerous questions posed by archaeologists about metal artifacts. The most frequent questions include:

∎ What is the nature of the metal or alloy which the object is made of?

∎ Where did the object and/or its raw materials originate?

∎ What technologies were employed in producing the object?

∎ How old is it?

Many aspects of a metal artifact's history are imprinted in its microstructure (i.e., the structure of the material as revealed under the microscope after appropriate surface preparation). The artifact has a story to tell and the role of the archaeometallurgist is to read and translate the story by studying and interpreting the microstructure. In most cases it is productive to supplement the information obtained from optical microscopy by using other analytical techniques. This will be illustrated below.

Although it is frequently not possible to obtain definitive answers to the above questions, this does not necessarily mean that the analysis has served no useful purpose. For example, it may be just as important to demonstrate what an artifact is not as to prove what it is. Eliminating some of the possible identifications may be a valuable contribution.

Consider the first question: What material is the artifact made of? It is normally essential to perform elemental analyses in order to identify the material. Nevertheless, metallography is a useful first step in answering this particular question. Furthermore, the specimen prepared for optical microscopy can be used without further preparation for other analytical techniques (such as electron probe microanalysis) which can yield an elemental analysis. As will be demonstrated in the following case studies, metallography is of great value in assessing the forms of impurities in metallic materials. This is highly useful information which elemental analysis cannot provide.

The word phytolith means “plant rocks.” Phytoliths are mineral deposits that form in and between plant cells. Any mineral deposit may be considered a phytolith, although most recent research has focused on opaline silica. Silica seems to be widespread in at least some plant families and is resistant to dissolution in a pH less than 9. Silica phytoliths therefore have the potential to be useful microfossils that can be helpful in the documentation of prehistoric environment and economy.

Identifiable shapes rather than amorphous deposits are a necessary characteristic for useful microfossils. Several plant families have long been known to be consistent accumulators of identifiable silica bodies: Gramineae (grass), Cyperaceae (sedge), and Equisetaceae (horsetail). Phytoliths from the Gramineae are especially well known; specialized silica-accumulating cells produce distinctively shaped phytoliths. However, other families have also been shown to produce significant amounts of identifiable phytoliths. Ulmaceae (elm), Fabaceae (bean), Cucurbitaceae (squash), and Compositae (sunflower) are a few examples of dicotyledonous families that commonly produce phytoliths. Some families, such as the Labiatae (mint), have yielded little or no identifiable phytoliths to date. However, further study may indicate phytolith production in particular species.

In the analysis of object or material form and structure, especially micro-structure, correlations of material properties with their microstructure, and of structures with their production history and function, are at the heart of much of artifact and fossil analysis in archaeometry. Presently, a great deal of such examination of archaeomaterials is either:

∎ qualitative, descriptive and anecdotal, comparing “representative” specimens to illustrate the differences of mean, typical, or normative structures, and forms; or

∎ limited to measurement of parameters which oversimplify the structure or are easily measured by hand, e.g., length, width, and thickness.

These do not differentiate shape variation or describe irregular shapes effectively. Hand measurements, even simple ones, are often difficult to derive on microstructures or on irregular macroscopic-sized objects and normally involve too few data points for statistical interpretation. Images of tesselated mosaics and multiphase microstructures in materials such as metals or ceramics are often chaotic and irregular in form, size variation and distribution of elements, inclusions and phases. Because of this, they are difficult to quantify precisely or accurately. Moreover, analysis is often limited more by the need to minimize destruction to an irreplacable artifact or art object than by a method's ability to generate significant data. Sample size is often held at the minimum threshold of significance or adequacy. Thus, any method which enhances the quality and quantity of such data should be welcome in archaeometric research.

Archaeologists have used microscopes to study traces of use on the edges of prehistoric stone tools for many years, but the past decade has seen a tremendous increase in the technical sophistication and substantive contributions made by this branch of archaeological research. Our purpose is to summarize the basic approaches archaeologists take to microwear analysis, the potentials of these approaches, and the kinds of traces that microwear analysts examine.

Three forms of microwear analysis can be identified and are based on (1) the range of magnification, (2) the type of equipment, and (3) the type of traces examined. The first relies on stereoscopic microscopes, works at magnifications ranging from 10 to 75×, and examines patterns in the abrasion and chipping of tool edges during use. More recent research indicate s that important variation also exists in the way a tool surface is polished during use, and the second analytical approach examines differences in polish appearance as well as utilizing the techniques of the first method. Microwear polishes are visible at magnifications from 100× to 400× using binocular microscopes and incident illumination. Finally, the third approach relies on the scanning electron microscope (SEM) and very high magnifications to identify traces of materials on which the stone tools were used. In this discussion we emphasize the first two of these analytical approaches because very few analysts have used the SEM.

The Von Hippel Award, the most prestigious award of the Materials Research Society was first presented to its namesake, Arthur von Hippel, in 1976. On November 19, 1988, Prof. von Hippel celebrated his 90th birthday, an appropriate occasion to look back on a lifetime of achievement. Through the many testimonials that were heard at his 90th birthday celebration from family, friends, former students and colleagues, emerged a picture of materials science that reflects much that we treasure as the fabric of the Materials Research Society, namely the interdisciplinary approach to materials research.

It has become an annual tradition of MRS to celebrate the achievement of the Von Hippel Award winner, and each year the celebrants begin the ceremony with an affirmation of the efficacy of the interdisciplinary approach. In the early years of the Von Hippel Award, our young students often heard greetings from Prof. von Hippel himself during the opening ceremony. But as the size of the meetings has grown, it has become increasingly difficult for “The Professor” to offer personal greetings. Many young people today yearn for contact with their intellectual heritage. Inspired by this need, the leadership of MRS recommended that a brief article be written for the MRS BULLETIN on reminiscences about Prof. Arthur von Hippel and his legacy of the interdisciplinary approach to materials research.

The 1989 Spring Meeting of the Materials Research Society will be held at the Town and County Hotel in San Diego, with events spanning April 22-29. Meeting Chairs Robin Farrow, Dick Siegel and Angelica Stacy have developed a program of 16 technical symposia that reflect the continuing key role of materials science in the development of both mature and emerging technologies.

Several new topics will reflect emerging areas, including materials for optical storage of information (Symposium F), ultrathin magnetic films (Symposium G), and materials problems of infrastructure (Symposium P). A special workshop will provide a technology update on diamond films (Symposium P) and will feature a joint session with Symposium H, Optical Materials: Processing and Science.

Plenary speaker Linus Pauling, research professor at the Linus Pauling Institute of Science and Medicine, will discuss quasicrystals, materials whose atomic structure displays perfect five-fold symmetry, but whose atomic pattern is never exactly repeated as it would be in conventional crystals. During the Plenary Session MRS will also recognize graduate students who have made outstanding contributions as authors or co-authors of papers presented at the 1989 Spring Meeting.