Applied Mineralogy

Minerals have been used in a number of various ways from time immemorial. Man has been using minerals even when he didn’t know its definition. Hence with the progress of civilization the concern about minerals slowly increased and it is this concern which gave birth to the science of mineralogy. Mineralogy is narrowly defined as the science of minerals. Moreover the scope of this subject covers a much wider range which encompasses mineral definition, origin, structure, properties and their impact on environment and applications in modern industry. Now human civilization is just indispensable without minerals. So before investigating the various aspects of mineralogy in details, let‘s have a closer look into the history and development of the science of mineralogy.

A mineral, by definition, is any naturally (not man-made) occurring inorganic (not a result of life plant or animal) substance. Its chemical structure can be exact, or can vary. All minerals belong to a chemical group, which represents their affiliation with certain elements or compounds. The science of mineralogy has spanned over several decades owing to its importance in various aspects. Knowledge of minerals of variable sources becomes essential for its application in metallurgy, gem-industry etc.

Crystallography is the study of the structure of crystals. It describes the structure of a crystal, the principles that govern the different types of possible structures, the crystal structures of specific substances, and the methods by which structures are determined. In numerous scientific fields, the knowledge of crystallography is essential and significantly important e.g. metallurgy, materials science, ceramics, physics and chemistry. Each of these fields has its own special requirements, but there is a basic core of knowledge common to them all. This consists of the description of the crystal structure in terms of the smallest unit representing it, the three-dimensional lattice with which the atom sites can be represented, and also the accepted method for determining planes and directions in crystal structures. Various aspects of crystallography e.g. symmetry, point groups and space groups, Miller indices, unit cell geometry, lattice, motif, planes and directions, crystallographic systems and forms, various crystal defects and symmetrical intergrowths of crystals called twinned crystals will be discussed to explain the crystal morphology and how it influences the various physical and chemical properties of minerals.

The Earth is composed of rocks. Rocks are aggregates of minerals. Minerals are composed of atoms. In order to understand rocks, we must first have an understanding of minerals. In order to understand minerals we must have some basic understanding of atoms—what they are and how they interact with one another to form minerals. A particular mineral cannot be formed unless the chemical ingredients necessary to make the mineral are present. Thus, the most common minerals are those that have a chemical composition made of the common elements found in their environment. The atomic bonds of minerals, rules governing the chemistry of the minerals, the different modes of their formation, inter-relationship between mineral species form the basis of mineral chemistry and shall be discussed in this chapter.

Both the physical properties of minerals and gemstones and their beauty are dependent on their chemical composition and atomic structure. Physical properties can be useful in distinguishing between both mineral species and individual minerals within a group or series.

Optical mineralogy is the study of minerals by measuring their optical properties. Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope. Optical mineralogy is used to identify the mineralogical composition of geological materials in order to help reveal their origin and evolution. Some of the properties and techniques used include: refractive index, birefringence, Michel-Lévy colour chart, pleochroism, extinction angle, conoscopic interference pattern and Becke line test—to be covered in this chapter

The specific properties detected in definite minerals are the function of mineral structures. The properties are useful in identification of these minerals and have important applications in various fields.

Descriptive Mineralogy should include first of all a description of the crystallographic, general physical and chemical characters of each mineral species, and should further give an account of its mode of occurrence and characteristic associations. In the case of minerals possessing an economic value, a brief statement of their uses is of interest.

Energy partition during mineral formation and subsequent recrystallization is controlled by thermodynamics. The minimum energy configuration gives the stability of a phase. To understand a system in terms of thermodynamic laws, energy distribution, entropy change is explained in this chapter.

Mineral formation process goes through many changes depending on the environmental condition (P-T) and elemental variation, available. On the basis of different P-T regime and mode of formation, mineral genesis has been grouped under igneous, sedimentary and metamorphic processes. Various aspects of these processes are explained here.

This chapter will deal with the formation processes of mineral deposits, i.e. the minerals that can be extracted economically and profitably and are commonly designated as economic minerals. Minerals are important because they contain most of the elements we use. All the minerals found in nature however do not fulfill this criterion. There are a number of factors which categorize a mineral as an economic one. The most important of these is that an economic mineral is needed to be easily extractable and economically viable. For example iron can be found in a number of minerals, but it is hematite and magnetite, which are particularly important from economic point of view. Two categories of minerals fall under this group – ore minerals and industrial minerals. The economic feasibility of minerals also varies with their diversified zones of formation, which actually largely control their characteristics.

At the new millennium, utilization of marine minerals is accelerating and knowledge of new types of marine mineral resources is expanding with significant present and potential scientific and economic benefits. The utilization of marine minerals is driven by growing societal and industrial needs, which may be met by turning to the sea for materials that are in short supply, strategically vulnerable,environmentally sensitive to recover on land, or can be recovered more economically from the seafloor. So a clear concept about the variety of minerals obtained from different marine regimes, their extraction, utility and the overall impact on environment has been concise in this chapter.

Mineral assemblages and textures may provide information about the conditions at which a rock equilibrated. In metamorphic rocks, we use qualitative terms such as low-grade, medium-grade and high-grade (and even ‘medium-low’ or ‘very high grade’) to describe the approximate temperature conditions of metamorphism. These designations do not provide information about pressure,and are therefore not useful for describing subduction zone rocks. Other methods for characterizing metamorphic conditions include: (a) Index minerals: Characteristic minerals that provide an indication of the temperature (and, in some cases, pressure) conditions at which a rock is formed (e.g., kyanite in metamorphosed shale; magmatic epidote in plutons and volcanic rocks).Not all rocks have a suitable bulk composition to produce index minerals.(b) Metamorphic facies: Assemblages of minerals, each characteristic for a particular bulk composition and indicating the range of pressure-temperature conditions at which the rock equilibrated. For example, high-pressure and lowtemperature conditions characterize the blueschist facies. Some igneous assemblages are also characteristic of crystallization within particular ranges of temperature/pressure conditions. This chapter deals with the determination of these methods.

Analytical instruments now-a-days become an essential part of mineralogical studies. With increasing instrumental sophistications, the details of mineral interactions are opening up. An idea of these studies is briefed in the present chapter.

Exploration geology is the process and science of locating valuable mineral or petroleum deposits, i.e., those which have commercial value. The term “prospecting” is almost synonymous with the term “exploration”. The exploitation of the vast mineral reserves to meet the growing requirements for a variety of applications has been a major economic activity, contributing significantly to a country’s industrial development and export trade. If bedrock is exposed anywhere at or around a prospect, then surface bedrock mapping is an essential beginning step for an exploration programme. This would include mapping and sampling (field geologic methods). This work focusses on identifying and mapping outcrops, describing mineralization and alteration, measuring structural features (geometry), and making geologic cross sections. Geochemical methods involve the collection and geochemical analysis of geological materials, including rocks, soils and stream sediments. The results mapping and sampling may suggest patterns indicating the direction where an ore deposit could be present underground or at the surface. Geophysical methods focus on measuring physical characteristics (such as magnetism, density or conductivity) of rocks at or near the earth’s surface. The measured values are then used to compare with the values and models of known ore deposits. A closer look on all these methods will be given in this chapter.

Experimental work involves simulating igneous or metamorphic conditions with specialized machines. Samples may include synthetic minerals or mixes of minerals, fluids such as H2O and/or CO2 or actual rock compositions. In the lab, samples of a known composition can be held at known pressure and temperatures, and results can be analyzed. Certain processes (melting, crystallization, diffusion) can also be simulated. All these processes leading to synthetic mineral preparation will be discussed in this chapter.

The growing need of minerals in industries and development lead to the need of understanding the subject more intensely. Various industrial applications and broad beneficiation techniques of different minerals are discussed in this chapter which will help to comprehend the potentiality of minerals in the realm of industrialization.

Minerals have a profound effect on environment. Study of minerals in details, i.e. mineralogy help to ascertain different problems and their causes which environment is facing on regular basis. This chapter deals with these major causes and hazards of environment, caused by minerals.

Mineralogical factors of an environment have mainly some negative (irritating, toxic) effect on human health. Mineral–induced pathogeneses can be caused by a distant effect (radiation), a tactile one (contacting with easy soluble toxic minerals), through pneumonic (pneumoconiosises–silicosis, anthracosis, asbestosis, etc.) or food (toxic and traumatic exposure of mineral particles in the digestive tract) effects of minerals. The most natural reactions of a living organism on the interacting mineral individuals and aggregates are, commonly, destruction, rejection or conservation. The whole field of medical mineralogy includes preventive measures, mineralogical diagnostics of diseases, the mineralotherapy (psychotherapy and physiotherapy), mineralogical pharmacology, application of minerals in traumatology and as constituents of implantants, the mineral tooling and medicinal topomineralogy, which helps in prospecting deposits and resources of drug minerals.