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Preface
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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Summary
Over the past two decades, many curriculum changes have occurred in geology, Earth science, and environmental science programs in universities. Many of these have involved the compression of separate one-semester courses in mineralogy, optical mineralogy, and petrology into a single-semester offering that combines mineralogy and petrology, commonly called Earth Materials. Such a course is a challenge to the instructor (or a team of instructors) and the students. This is especially so when few, if any, textbooks for such a one-semester course have been available.
This text, Earth Materials, is an introduction to mineralogy and petrology in which both subjects are covered with a roughly even balance. To keep this textbook reasonably short and applicable to a one-semester course, we decided against providing a shallow survey of everything and instead concentrated on what we consider the most fundamental aspects of the various subjects.
In the writing of this text, we assumed that the students who enroll in an Earth materials course would have previously taken an introductory physical geology course, as well as a course in college-level chemistry.
Coverage
Basic aspects of mineralogy must precede the coverage of petrology. This sequence is obvious from the chapter headings. After a brief, general introduction in Chapter 1, minerals and rocks are broadly defined in Chapter 2. That is followed by three chapters that relate to various mineralogical aspects and concepts. Chapter 3 covers the identification techniques that students must become familiar with to recognize unknown minerals in the laboratory and in the field. It also includes discussion of two common instrumental techniques: X-ray powder diffraction and electron beam methods. Chapter 4 covers the most fundamental aspects of crystal chemistry, and Chapter 5 is a short introduction to basic aspects of crystallography. Chapter 6 covers optical mineralogy. This subject is included so that instructors who plan to introduce thin sections of rocks in their course can give their students quick access to the fundamentals of optical mineralogy and the optical properties of rock-forming minerals.
The sequencing of subsequent systematic mineralogy chapters is completely different from that most commonly used in mineralogy textbooks. In these chapters, minerals are discussed in groups based first on chemistry (native elements, oxides, silicates, and so on) and, subsequently, for the silicates, on structural features (layer, chain, and framework silicates, and so on).
3 - How Are Minerals Identified?
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp 37-60
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Summary
The ability to recognize common minerals in hand specimens is basic to much that follows in this text. The tests that you will become familiar with are exactly the same as those used worldwide by field and research geologists, be it in the field, in the research laboratory, or in the home office. Your course instructor may discuss the various techniques for the unique identification of a mineral (or several minerals as in a rock) in lectures, but personal expertise can be gained best by hands-on work that you will likely do in the laboratory that accompanies your course. There you will have small test samples that you will be allowed to scratch (to test hardness), to hold in your hand (“to heft” the specimen so as to assess its average specific gravity), and to evaluate their reaction to dilute HCl, and so on. Even better is that you will probably also see much larger, better mineral hand specimens in which you can observe other properties such as crystal form, habit, cleavage, range of color, and state of aggregation. You will learn to combine these observations and develop the skills to identify unknown minerals correctly.
Once you know what mineral you are dealing with, or which several minerals, as most common rocks contain a mix of minerals, you will be well prepared for understanding how rocks are classified and the conditions under which different rock types (igneous, sedimentary, and metamorphic) are formed. For example, once you have identified all four major minerals in a specific, relatively coarse-grained, light-colored rock as (1) quartz, (2) two types of feldspar, and (3) a mica, you can conclude that you are dealing with a granite. Such knowledge of common rock-forming minerals is basic to much of what is presented in this text. The four later chapters that deal with the systematic mineralogy of igneous rocks (Chapter 7); sedimentary rocks (Chapter 11); metamorphic rocks (Chapter 14); and ore deposits, coarse-grained pegmatites, and quartz veins (Chapter 16) give detailed information on the diagnostic properties that allow us to identify minerals.
We introduce you to various observations and tests that can be made of minerals in hand specimens. In many instances a combination of the results of several of these leads to the identification of the mineral at hand.
Minerals and Varieties
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp 571-572
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Index
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp 577-594
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9 - How Do Igneous Rocks Form?
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp 241-278
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Summary
Igneous rocks are the most abundant rocks in the Earth's crust, formed by the crystallization of melts that have risen from the planet's interior. The crust itself has formed over an extended period of time, in fact billions of years, by just such crystallization. The outer half of the planet is normally solid, so it is natural to wonder where magmas come from. Where does this melting take place, and why do normally solid rocks become molten? What composition do rocks have in the source region? Is melting partial or total? What magma compositions are formed when these rocks melt? What makes magma rise toward the surface, and how fast does it travel? As magma ascends and begins to cool, it becomes a mixture of liquid and crystals that can separate from one another and change the composition of the magma. Eventually, magma cools and solidifies to form igneous rock. The processes leading to the formation of this rock are of great importance because they have controlled the differentiation of our planet. The composition of the crust is very different from that of the planet as a whole, and life as we know it would be very different if these processes had not taken minor elements from the Earth's interior and concentrated them in the crust. In this chapter we look into each of these igneous rock-forming processes. We leave to Chapter 10 a discussion of the diversity and classification of igneous rocks.
Igneous rocks are those formed by the solidification of molten rock. This molten material, which we call magma, is formed at depth in the Earth and rises toward the surface, where it cools and solidifies, either beneath the surface, where it usually has time to crystallize, or on the surface as volcanic rocks, where cooling may be rapid enough to form glass. We classify igneous rocks on the basis of the minerals they contain, which reflect the composition of the magma. Magma compositions are determined in the source region by the type of rock that undergoes partial melting, but they can be modified during ascent and solidification, especially in large magma chambers, where solidification can take thousands of years. Throughout geologic time, the rise of magmas from the mantle has slowly generated the Earth's crust, whose composition is therefore determined by the composition of magmas.
Common Units of Measure
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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13 - Sedimentary Rock Classification, Occurrence, and Plate Tectonic Significance
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp 385-414
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Summary
In the previous chapter, we looked at how sediment is formed, transported, deposited, and lithified to form rock. In this chapter, we discuss the classification of sedimentary rocks, which fall into three main groups: (1) the siliciclastic sedimentary rocks, which include mudrocks (shale), sandstones, and conglomerates; (2) the biogenic sedimentary rocks, which include limestones, dolostones, cherts, and coals; and (3) the chemical sedimentary rocks, which include evaporites, phosphorites, and iron-formations. We learn how each type can be identified and examine the textures of the most important types in photomicrographs of petrographic thin sections. Correct identification of sedimentary rocks is the first step to working out the geologic history of an area, because these rocks preserve a record of the source of sediment, its mode of transport, and its site of deposition, which in many cases is determined by plate tectonic processes. We examine the geologic record preserved in some specific sedimentary rock sequences. Sedimentary rocks are the source of all fossil fuels, most iron ore, material used for fertilizers, much of the world's gold ore, and many other placer mineral deposits. Most of the world's construction material comes from sediments and sedimentary rocks in the form of building stones and raw material (lime and aggregate) for making cement. Porous sedimentary rocks form important aquifers both for agricultural use and for sustaining urban areas. In this chapter, we indicate with which sedimentary rocks each of these economically important resources is associated. We also discuss the plate tectonic setting in which each sedimentary rock is formed.
Sedimentary rocks are formed from the lithification of sediment (Fig. 12.1). They are classified into three main groups based on the type of sediment from which they are formed. Those formed from the detritus of weathered rocks are called siliciclastic because most of their minerals are silicates. Those formed from sediment derived from organisms are described as biogenic, and those formed by chemical precipitation are referred to as chemical sedimentary rocks.
Acknowledgments to Second Edition
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp xix-xx
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11 - Sedimentary Rock-forming Minerals and Materials
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp 333-352
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Summary
This chapter presents the systematic descriptions of uniquely sedimentary rock-forming minerals and materials. These are mainly the newly formed minerals that result from interactions of preexisting minerals with the atmosphere or precipitation from the oceans. Detrital minerals such as quartz, feldspar, and the micas, which were discussed in Chapter 7, are the major constituents of sedimentary rocks such as sandstones, arkoses, and graywackes. By studying hand specimens of these minerals in the laboratory while referring to the appropriate specimen descriptions in this chapter, you will further develop your mineral identification skills.
In chapters 7, 9, and 10, we address many aspects of minerals and rocks of igneous origin. They are the result of crystallization from a liquid magma over a wide range of high temperatures (~1400 to 600°C) in an environment in which oxygen gas (O2) is nonexistent and in which H2O is generally a minor constituent. This chapter deals with minerals that (1) are newly formed as a result of chemical reactions (under atmospheric conditions) that slowly destroy earlier minerals (e.g., feldspars) and recombine various ions in solution in water to form clay minerals, and oxides or hydroxides, and (2) those that are chemical precipitates in depositional basins such as carbonates, evaporite minerals, and Precambrian iron-formations. However, we must also mention those minerals that have survived the physical and chemical weathering processes while exposed to the atmosphere; these are known as detrital minerals.
We systematically treat 13 sedimentary rock-forming minerals. These include ice, the solid form of H2O; a hydroxide; a clay mineral (representative of the large clay mineral group); two polymorphs of CaCO3; four more carbonates; two halides; and two sulfates. Clearly, this group of common sedimentary minerals is totally different from the igneous rock-forming minerals discussed in Chapter 7.
We close with discussions of three sedimentary materials: chert and agate, phosphorite, and soil.
12 - Formation, Transport, and Lithification of Sediment
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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Summary
Sedimentary rocks form through the compaction and cementing together of loose sediment, which can be derived from the weathering of preexisting rocks, the hard parts of organisms, or chemical precipitates. Most sediment is formed from weathered rock, and this detrital material must be transported by water, wind, or ice to depositional sites before it can begin the process of turning into solid rock. Grain size is an important property of sediment because it determines how easily sediment can be moved. During transport, sediment is sorted by grain size. In rivers, which are the main agent of sediment transport, the coarser fraction travels on the bottom, whereas the finer fraction travels in suspension, which leads to separate deposits of coarser sand and gravel and finer mud, respectively. Most detrital sediment is transported to the sea, but some accumulates in basins on continents. Along shorelines, wave action further abrades and sorts sediment. In warm climates, coastal sediments may consist almost entirely of the hard parts of calcareous organisms. Sediment eventually accumulates in basins, most of which have a specific plate tectonic setting, such as forearc basins at convergent plate boundaries, subsiding passive continental margins, and rift and pull-apart basins on continents. Sediments accumulating in these basins begin to compact under their own weight as pore fluids are expelled. These fluids are commonly saturated in the minerals with which they are in contact, and as the fluids rise, they precipitate minerals that cement the detrital grains together to form a rock. In this chapter, we discuss the formation, transport, deposition, and eventual solidification of sediment to form sedimentary rock.
Importance of Sediments in Understanding the History of the Earth
Sedimentary rocks, which are the topic of Chapter 13, are formed by the accumulation and burial of sediment in depositional basins. Most sediment is formed from the weathering of preexisting rocks as a result of physical, chemical, and biological processes. Some sediment is formed directly by organisms, and some may be a direct chemical precipitate. Sedimentary rocks have a diverse compositional range, not only because of differences in the type and source of the sediment but also because of processes associated with the transport and burial of sediment. Before we discuss sedimentary rocks, we must, therefore, understand how sediment is formed, transported, deposited, and turned into rock (Fig. 12.1).
Frontmatter
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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Acknowledgments to First Edition
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp xviii-xviii
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15 - Metamorphic Rocks
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp 439-476
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Summary
Metamorphism includes all changes that affect rocks as a result of changes in pressure, temperature, or composition of fluids in the environment. These changes occur in sedimentary, igneous, and even former metamorphic rocks. The Earth's tectonic plates are constantly on the move, and consequently most rocks experience change at some time in their history. Metamorphic rocks are abundant, constituting approximately 60% of the continental crust. Even igneous rocks of the ocean floor are metamorphosed by circulating ocean water that cools them near midocean ridges. Metamorphic rocks preserve an important record of past conditions in the lithosphere, so it is important that we learn how to read that record. In doing this, we address the following important questions: Why do metamorphic rocks change when they find themselves in a new environment? Do these changes go to completion; that is, do they reach equilibrium under the new conditions? Do minerals in the rock tell us what those conditions were? And what are the chances that new minerals formed at depth in the Earth survive the trip to the surface during exhumation? We will learn that metamorphic rocks closely approach thermodynamic equilibrium and, as a consequence, contain only a small number of minerals. Mineral assemblages can be used to determine pressures, temperatures, and fluid compositions at the time of peak metamorphism. These assemblages are normally preserved during exhumation. Textures of metamorphic rocks provide important information about stresses in the crust during metamorphism.
Metamorphism is the sum of all changes that take place in a rock when it experiences changes in temperature, pressure (both lithostatic and directed), or composition of fluids in the environment. The important word in this definition is change. The changes may be physical, chemical, or isotopic, or any combination of these. The original rock, known as the protolith, can be igneous, sedimentary, or a previous metamorphic rock. Most metamorphic reactions are very slow, so time is important to determine how complete a change may be. Some rocks are more reactive than others, and higher temperatures and the presence of fluids also speed up reactions. Changes that take place while rocks are heating are referred to as prograde and those occurring during cooling are referred to as retrograde.
8 - The Direction and Rate of Natural Processes: An Introduction to Thermodynamics and Kinetics
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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- 15 December 2016, pp 197-240
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Summary
Have you ever wondered why change occurs and why some processes are rapid whereas others are slow? Why does a match burn when struck, or why does a tombstone weather? Both processes involve reaction with oxygen in the air, but the match burns rapidly, whereas the tombstone weathers slowly. Why should the match or the tombstone react with oxygen, and why do the processes have such different rates? In this chapter we examine the fundamental principles governing all change. Thermodynamics is the subject that provides the answers to the questions about the direction of natural processes, whereas kinetics deals with the rates of processes. Thermodynamics is the study of energy and its transformations. It allows us to determine the direction of natural process and the equilibrium states toward which they strive. The rates of natural processes vary considerably, from the rapid explosion of volcanic gas to the slow motion of tectonic plates. Despite this great variation, these processes obey similar laws. We will also introduce some of the fundamental thermodynamic principles that allow us to determine what to expect if equilibrium were achieved. We then outline some of the important factors that control the rate at which equilibrium is approached. Finally, we look at one of the most remarkable rate processes, that of radioactive decay, and how it is used to determine absolute ages.
The elements that constitute the Earth can combine in a large number of ways to form many different minerals, which, in turn, can combine in different ways to form many different rocks. In addition, one set of elements might form one mineral under one set of conditions and another mineral under another set; e.g., graphite and diamond are both forms of carbon (polymorphs, see Sec. 5.8), but graphite is the stable form at low pressure and diamond the stable form at high pressure. Or a group of minerals that form a rock under one set of conditions might change into a different group of minerals, or even melt, under another set of conditions (Chapter 15). And under still other conditions these minerals may weather and be transported and deposited as sediment (Sec. 11.17).
10 - Igneous Rocks: Their Mode of Occurrence, Classification, and Plate Tectonic Setting
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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Summary
The aim of this chapter is to introduce the main types of igneous rock and their modes of occurrence. We classify igneous rocks according to their mineral content as well as by their texture, which varies according to whether the magma solidifies slowly beneath the surface or rapidly on the surface. We accordingly start the chapter by discussing where magmas cool and solidify and the types of igneous bodies formed. We then discuss the classification of igneous rocks using the scheme proposed by the International Union of Geological Sciences. Although many igneous rocks have been found and named, the vast majority are described by only a few names, and these rocks form common associations that can be related to their plate tectonic settings. We discuss and illustrate examples of the main rock types in each of these associations and explain why each forms in its particular setting. We end the chapter by discussing three unusual rock associations, two were formed only in the Precambrian, and the third was formed by large meteorite impacts.
So far in this book we have classified rocks into igneous, sedimentary, and metamorphic, and we have discussed the origin of magmas and igneous rocks using only a few common rock names, such as basalt, andesite, and granite. In this chapter, we consider the classification of igneous rocks in more detail, and we see, for example, that some rock types commonly occur together, whereas others are never associated. In Chapter 9, we learned about igneous rock-forming processes – why rocks melt, where they melt, and how they melt. We saw that the melting process controls the composition of the liquid, which determines the composition of magmas that ascend into the crust. We also learned about the physical properties of magma and of processes that can change its composition and, hence, the spectrum of igneous rocks it can form. We are now in a position to use this knowledge, first, to describe where igneous rocks form; second, to learn how igneous rocks are classified; and finally, to relate igneous rocks to plate tectonics.
18 - Earth Materials and Human Health
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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Summary
In this chapter, we briefly examine how Earth materials affect human health. A moment's reflection will convince us that our bodies and their well-being are intimately related to Earth materials. Most of the elements in our bodies are derived from soil, which in turn is derived from the weathering of rock. Humans have evolved to be in harmony with what the Earth's surface provides. Our food ultimately comes from vegetation, which depends on the soil and climate for growth. On occasions, and in certain regions, conditions can change from the norm as a result of natural processes or stresses placed on the planet by human activity, and these changes can adversely affect our health. When Earth materials are mentioned in connection with human health, we immediately think of major environmental problems, because these attract so much attention in the press, but Earth materials affect our health daily and, for the most part, beneficially. In some areas, however, certain Earth materials pose a serious health hazard, and on rare occasions, such as during the eruption of a volcano, Earth materials can pose serious and catastrophic hazards to humans.
The effect of Earth materials on human health is a huge topic, and we can address only a few important highlights in this chapter. We start by looking at how Earth materials are beneficial to our health, and then we examine some serious problems that they can pose. We finish with catastrophic hazards resulting from volcanic eruptions and the extremely rare occurrence of meteorite impacts.
In this book, we have discussed the important minerals and rocks that constitute our planet, how they form, and where they occur. We have also discussed their use as ore minerals, building materials, and sources of energy. However, Earth materials affect us in a more direct and personal way through our health. Our bodies, like those of all other living organisms, have evolved to use Earth materials for their construction and function. In this chapter, we briefly examine which Earth materials are important for good health and which can cause chemical and physical threats to our well-being. We have room to touch on only a few highlights of this extremely important field.
14 - Metamorphic Rock-forming Minerals
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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Summary
This chapter, like Chapters 7 and 11, provides systematic descriptions of minerals but only for those that occur most commonly in metamorphic rocks. As was noted already, the best way for you to acquire basic skills in mineral identification is to read each mineral description while you have one or several examples of this same mineral on a tabletop where you are working. Clearly, this is best accomplished in a place where your instructor has mineral collections available for study. In most courses, this is in the laboratory that accompanies the course. Observe, study, and handle as many examples of the same mineral species as are available. If possible, also look at coarse-grained examples of metamorphic rocks that may contain some representative metamorphic mineral associations.
This chapter presents the systematic mineral descriptions of 26 of the most common metamorphic minerals. All of these are silicates except for one, corundum, an oxide. Such minerals are the result of chemical reactions involving preexisting minerals in sedimentary, igneous, or metamorphic rocks. These reactions may result from changes in temperature, pressure, fluids, and shearing stress at considerable depth in the Earth (see Chapter 15). Mineral reactions that are the result of an increase in temperature are referred to as prograde, whereas those that result from falling temperatures are retrograde. Retrograde metamorphic reactions commonly involve the addition of fluids.
Systematic Mineralogical Descriptions of Common Metamorphic Minerals
The order in which metamorphic minerals are discussed in this chapter reflects their relative abundance. We begin with minerals that are common in some of the most abundant metamorphic rock types. An example of such an abundant rock type would be what is known as a pelitic schist. A pelitic schist is a rock derived by metamorphism of an argillaceous (meaning composed of clay-sized particles or clay minerals) or fine-grained aluminous sediment. Prograde metamorphic reactions in such a rock may produce sequentially metamorphic assemblages rich in chlorite and muscovite; subsequently garnet–staurolite–biotite–muscovite assemblages; and at the highest temperature, sillimanite–garnet–cordierite–feldspar assemblages. Members of the mica group (muscovite and biotite) and the feldspars are major constituents of these meta-morphic rocks but their systematic descriptions are given in Chapter 7 because they are also major constituents of igneous rocks.
Plate section
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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5 - Introduction to Crystallography
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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Summary
When minerals occur as well-developed (euhedral) crystals, they reveal symmetry. Figure 2.5(B) shows garnets as perfect dodecahedra (a special form in the isometric system). Figure 2.6 shows very well-formed but less symmetric crystals of green microcline, and Figure 2.8 shows four different crystals with very different outward appearances and symmetry contents. These well-developed crystals are the outward expression of the underlying internal order of their crystal structures.
Symmetry deals with repetition of objects (atoms, ions, ionic groups) through reflection, rotation, inversion, and translation. The study of the external form and the crystal structure of crystalline solids and the principles that govern their growth, shape, and internal atomic arrangement is called crystallography. Here we begin with aspects of the external symmetry (morphology) of crystals, because this is generally simpler to evaluate than the more complex symmetry content of the underlying crystal structure. We proceed with that in Section 5.7 of this chapter.
The basic aspects of crystallography that are described in this chapter are probably new to most readers. Chemical concepts that were treated in Chapter 4 were mostly not new because of earlier chemistry courses. In crystallography, very basic aspects such as symmetry elements are later incorporated into more complex concepts. In other words, earlier learned materials sequentially build into later, conceptually more difficult ideas.
We begin with symmetry elements that can be seen in well-formed (euhedral) crystals. We subsequently assess combinations of symmetry elements and see how these can be grouped and referred to various sets of reference axes. This then leads to what are called crystal classes (or point groups). And yet further on, we evaluate symmetry elements and translations in crystal structures, instead of just those that are represented by morphological crystals.
This necessary, sequential approach is best expressed by the concept map that follows:
Symmetry Elements and Operations
The geometric feature that expresses the symmetry of an ordered arrangement is known as a symmetry element. The process that results in this symmetry element is known as a symmetry operation. Although these terms imply motion, the faces on a crystal or the atoms inside a crystal structure do not move.
2 - Materials of the Solid Earth
- Cornelis Klein, University of New Mexico, Anthony Philpotts, University of Connecticut
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This chapter introduces minerals and rocks, the solid building materials of planet Earth. We define minerals and rocks and give examples of each from common daily uses. The main purpose of this chapter is to explain what minerals and rocks are with minor reference to specific names. Although we use several rock and mineral names in giving examples, these need not be memorized, because we encounter them in later chapters. In this chapter, it is important to understand what minerals and rocks are and to appreciate their differences. The examples of minerals and rocks that we encounter on a daily basis are given simply to emphasize the importance of Earth materials to our daily lives. Indeed, human cultural evolution is normally classified on the basis of the Earth materials used for making tools (e.g., Stone Age, Bronze Age, Iron Age). Although we have benefited from the use of Earth materials, some materials pose potential health hazards (e.g., asbestos). Rocks have provided the main source of construction material for large buildings throughout history, and even though modern buildings are mostly made of concrete and steel, the concrete is made from limestone. We end the chapter with a brief discussion of where rocks are formed. Rocks are the direct product of plate tectonic processes, and characteristic sets of igneous, sedimentary, and metamorphic rocks form in specific plate tectonic settings.
This text has the title Earth Materials. An inclusive definition of Earth materials encompasses the following: minerals and rocks, which are the solid parts; soils, the unconsolidated materials above bedrock; fossil fuels, which include all the hydrocarbons used for fuel and energy – petroleum, natural gas, and coal; the various forms of H2O, in salt water and freshwater, in glaciers and ice caps; and the atmosphere, the mixture of gases that surrounds the Earth.
This book is an introduction to the solid materials that compose the Earth, but short discussions of soils (Chapter 11), coal (Chapter 13), and fossil fuels (Chapter 17) are included.