Abstract This volume covers the topics related to the 13th EMU School ‘Layered Mineral Structures and their Application in Advanced Technologies’. All of the selected topics, the school, and this volume are thus aimed at providing an in-depth knowledge of the complex field of layered materials, with an attempt to address several fundamental aspects, which range from crystal chemistry and structure to layer packing disorder, from surface properties to the description of the most advanced experimental techniques useful in the characterization of layered materials. Layered materials, because of their particular atomic arrangement, are commonly characterized by physical and chemical properties of great interest in numerous technological and environmental processes and applications, as better detailed in the body of this volume. Most of these properties play a significant role in Earth sciences, environmental sciences, technology, biotechnology, material sciences and many other scientific areas. The surface properties of layered materials control important interaction processes, such as coagulation, aggregation, sedimentation, filtration, catalysis and ionic transport in porous media. Layered minerals also control many aspects of Earth's rheology, i.e. the movement of geological masses, at least as far down as the lower crust. Given this frameset, it should be no surprise that the extremely large field of investigation of these materials can, and in most of the cases must, be approached from several different viewpoints. However, providing full coverage of the immense literature devoted to all the topics above may be impractical, if not impossible.

ABSTRACT The precipitation of carbonate into alkalinc silicate solutions results in the formation of self-assembled crystal aggregates with noncrystallographic morphologies. These precipitates emulate biologically induced mineral textures as well as display forms typical of primitive microfossils. The precipitation behavior varies with pH, i.e., as a function of the species created by dissociation of the silicic acid under alkaline conditions. Calcite single crystals and crystal aggregates precipitated in these media display complex forms derived From the specific inhibition of some crystal faces, and eventually, noncrystallographic shapes such as sheaf-of-wheat with self-organized banding develop. When strontianite and witherite precipitate in these environments at pH higher than 10, their crystal aggregates display in addition very specific morphologies, such as target patterns, scrolls, twisted ribbons, spirals, fingers, etc., with typical sizes ranging from microns to millimeters. The crystallites of the metal carbonate are embedded in a silicate matrix and are co-oriented and parallel to each other, suggesting that both the loci for nucleation and the orientation of the carbonate groups are controlled by the silica phase. The silica concentration (>250 ppm SiO 2 ), ionic force, and pH values (>8.5) required for the phenomenon to be observed are well within the range of values measured in contemporary alkaline lakes. A number of geological scenarios where the phenomenon could occur have been identified, among which are: a) contemporary lakes and thermal springs associated with alkaline magmatism such as those in the African rift valley; b) Precambrian (particularly Archean) terranes where cherts formed as a result of direct precipitation of silica; and c) a scenario on Earthlike planets where the existence of a silica-rich environment derived From hydrolysis of alkaline rocks is predicted.

Abstract Electrical conductivity is the movement of electrical charge from one location to another. Because the charge may be carried by ions or electrons, whose mobilities vary from material to material, there is a full spectrum of conductivities ranging from highly conducting metals to nearly perfect insulators, as illustrated in Figure 1 Electrical conductivity can be derived from the relation where n is the number of charge carriers in a material, e is the charge carried by eachu is the mobility of the carriers. The mobility is defined as the drift velocity per unit electric field. Since the charge carriers may be ions or electrons (or “holes” as we shall see later), we classify conduction in solids as ioncc or electroncc within the range 1 to 10s mho/m. Below this range of conductivity, materials may be semiconductors or insulators. For porous media, such as rocks at the earth’s surface, conductors extend into the range normally covered by solid semiconductors. Ionic conductivity involves the ordered movement of ions in an electrolyte upon application of an external electric field. In the absence of an electric field, the ions move randomly as a result of thermal agitation and collisions with other ions and atoms. Since both cations and anions are present in an electrolyte, the conductivity can be expressed as where the numbers and mobilities of the positive and negative ions are indicated by superscript signs. A temperature increase results in a conductivity increase since the mobility of both ion species is