This issue of the MRS Bulletin is devoted to Earth materials — a subject so broad and with such a long history, stretching back to man's first use of materials, that we can offer only a small sample of topics, only a partial review. As our ancestors fashioned the first crude tools from stone, they must have distinguished among materials on the basis of their physical properties. They classified materials by color and density and very early must have wanted more than Nature had provided. They began to synthesize and fashion their own materials. Today's nanoscale engineering of materials is part of this same quest—a continuous evolution of this early toolmaking.

Thus, Earth materials were the first raw materials—and the first subjects of study and classification in materials science. Probably one of the earliest materials scientists to make quantitative observations was Nicolas Steno (1638–1686, actually Nils Stensen, a Dane by birth), who was among the first to note the “law of constancy of angle” in comments which accompany his drawings of quartz and hematite crystals (De Solido intra Solidum Naturaliter Conteno Dissertationis Prodromus, 1669). Such observations were the first clues to understanding the internal structure of solids. Steno was also a keen geological observer. He is given credit for the first statement of the law of superposition of sedimentary strata. The first quantitative experiments on the origin of minerals grew out of studies of glass and ceramics. French mathematician René-Antoine Ferchault de Réaumur (1683–1757) tried to determine the composition of Chinese porcelain by melting minerals and rocks.

As I write, it is about six years since Bednorz and Müller sent off their amazing paper reporting superconductivity at about 30 K for a mixed phase sample in the La-Ba-Cu-O system. After an incubation period of a few months, during which only a handful of people paid any attention, the community suddenly woke up (literally overnight) to the realization that the discovery was genuine, when Kitazawa (Tokyo University) and Chu (University of Houston) confirmed the result at the 1986 Fall Meeting of the Materials Research Society. No need to repeat the stories of the next frantic couple of years: the Nobel Prize for the discovery, the tantalizing prospect of another prize for understanding the superconducting mechanism, the almost limitless prospects of new superconducting technologies which appeared in article after article, designed not just for scientists and engineers, but for the general public at large. Now, six years later, perhaps some perspective on the high-temperature superconductivity discoveries is possible.

At the fundamental science level, the discoveries have indeed been spectacular. Many layered structures based on the CuO2 sheets have been discovered. The first advance was the Tokyo group's discovery of the structure and composition of the superconducting phase La2-xBaxCuO4-δ, where x is optimally about 0.15. Then came the Alabama/Houston discovery of superconductivity at 92 K in YBa2Cu3O7-δ, followed rather quickly by the discoveries of 110 K superconductivity in the Bi-Sr-Ca-Cu-O (BSCCO) system at Tsukuba and then 125 K in the Tl-Ba-Ca-Cu-O (TBCCO) system by the Arkansas group.

Nature is generous with complexity. The number of thermodynamic variables necessary to describe even simple stream chemistry can easily number to a hundred. Nevertheless, research on Earth materials remains exciting because of the vastness of geologic time and the huge scale of global processes. For example, even simple ion-exchange experiments have profound implications when considered in the context of global cycling of elements. Sodium exchange from seawater onto the 1.83 × 1016 g of river-borne clays removes 20–30% of the yearly sodium addition to the ocean. Research on Earth materials, although complex, is rewarding through the scale of the potential result.

The surface chemistry of minerals is important for understanding natural mineral transformations and also because surface reactions help control the migration and degradation rates of pollutants in natural waters. These pollutants range from organic herbicides and pesticides, which leak past reactive soil horizons into groundwaters, to acid rain and heavy-metal leaching from mine tailings, sewage sludge, or coal fly ash. The importance of characterizing mineral surface chemistry is clear when one considers that 0.5 to 2% of usable groundwater in the United States is thought to be contaminated.

This article reviews some simple surface chemistry of oxide and silicate minerals in water. We focus on the kinetics of mineral corrosion because this subject is interesting to both geochemists and materials scientists. The surface properties that make some solid oxides relatively inert to acid corrosion, for example, are also manifested in the rates of natural mineral weathering.

Materials science and engineering (MSE), as a field as well as a discipline, has expanded greatly in recent years and will continue to do so, most likely at an even faster pace. It is now well-accepted that materials are crucial to the national defense, to the quality of life, and to the economic security and competitiveness of the nation. Mankind has recognized the importance of manmade materials to the quality of life for many centuries. In many cases, the security and defense of tribes and nations have substantially depended on the availability of materials. It is not surprising that historical periods have been named after materials—the Bronze Age, the Iron Age, etc. The major requirements from materials in those days were their properties and performance. Today, in this age of advanced materials, the importance of materials to defense and quality of life has not changed. However, the critical role of materials has taken an additional dimension: it has become essential to enhancing industrial competitiveness.

The knowledge base within MSE has also expanded vastly throughout these years and continues to do so at an increasing rate. We are constantly gaining a deeper understanding of the fundamental nature of materials, developing new ways to produce and shape them for applications extending from automobiles to supersonic airplanes, optoelectronic devices to supercomputers, hip implants to intraocular lenses, or from household appliances to gigantic structures. We are also learning that, in many of these applications, we need to depend on the combinations or composites of different classes of materials (metals, ceramic, polymers, and electronic materials) to enhance their properties.

The use of materials based on their mechanical behavior has moderated key aspects of the development of civilization. Starting perhaps with stone and wood, used more or less in forms provided directly by nature, progressing to the ferrous metallurgies that gave birth to the entire industrial revolution, and continuing with today's exotic high-strength, light-weight alloys and composites, materials have frequently been selected to fulfill the structural engineering needs of designers, builders, and inventors. Following these trends, studies of the mechanical behavior of solids, once the exclusive purview of blacksmiths and artisans, came to occupy the attention of scientists and engineers worldwide, and were foundational to the modern discipline of materials science and engineering.

In this issue of the MRS Bulletin, we have selected five articles that highlight the intellectual coupling of traditional mechanical behavior investigations with the use of materials in thin film forms. Such a coupling is not entirely new. In an ASM-sponsored seminar held in 1963, for instance, one of the papers presented was entitled simply “Mechanical Properties of Thin Films.” Within the last decade, however, and due largely to developments within the microelectronic and magnetic disk industries, awareness of the need to predict, control, and understand the mechanical behavior of thin film media has grown rapidly. Many of the most important failure mechanisms operative in integrated circuits, for example, such as stress and electromigration voiding, are mechanical in nature.