矿物和矿物学 Minerals.pdf

Published in 2012 by Britannica Educational Publishing a trademark of Encyclopdia Britannica, Inc. in association with Rosen Educational Services, LLC 29 East 21st Street, New York, NY 10010. Copyright 2012 Encyclopdia Britannica, Inc. Britannica, Encyclopdia Britannica, and the Thistle logo are registered trademarks of Encyclopdia Britannica, Inc. All rights reserved. Rosen Educational Services materials copyright 2012 Rosen Educational Services, LLC. All rights reserved. Distributed exclusively by Rosen Educational Services. For a listing of additional Britannica Educational Publishing titles, call toll free 800 237-9932. First Edition Britannica Educational Publishing Michael I. Levy cutive Editor J.E. Luebering Senior Manager Marilyn L. Barton Senior Coordinator, Production Control Steven Bosco Director, Editorial Technologies Lisa S. Braucher Senior Producer and Data Editor Yvette Charboneau Senior Copy Editor Kathy Nakamura Manager, Media Acquisition John P. Rafferty Associate Editor, Earth and Life Sciences Rosen Educational Services Nicholas Croce Editor Nelson S Art Director Cindy Reiman Photography Manager Matthew Cauli Designer, Cover Design Introduction by John P. Rafferty Library of Congress Cataloging-in-Publication Data Minerals / edited by John P. Rafferty. 1st ed. p. cm. Geology lands, minerals, and rocks “In association with Britannica Educational Publishing, Rosen Educational Services.” Includes bibliographical references and index. ISBN 978-1-61530-582-7 eBook 1. Minerals. I. Rafferty, John P. QE363.2.M5479 2012 549dc22 2010044473 On the cover front and back Amethyst crystals. S On the cover front top, p. iii Examples of some popular minerals are granite stone left, black coal middle left, gold ore middle right, and marble stone right. Shutterstock. com On pages 1, 35, 77, 111, 187, 228, 247, 323, 326, 331 An array of apophyllite, stilbite and quartz crystals. S Contents 11 25 51 Introductionx Chapter1TheNatureofMinerals1 Nomenclature 3 Occurrence and ation 4 Mineral Structure 5 Primary and Accessory Minerals 6 Morphology 6 Internal Structure 9 Polymorphism 13 Chemical Composition 14 Mineral ulas 15 Compositional Variation 16 Chemical Bonding 19 Physical Properties 23 Chapter2MineralClassificationand Associations35 Classification of Minerals 35 Native Elements 37 What is a Native Element 37 Metallic Substances 51 Sulfides 53 Sulfosalts 54 Oxides and Hydroxides 55 Halides 57 Carbonates 59 Nitrates 61 Borates 62 Sulfates 63 Phosphates 64 Silicates 64 Mineral Associations and Phase Equilibrium 69 91 108 132 Assemblage and the Phase Rule 71 Phase Diagrams 73 Eh–Ph Diagrams 75 Chapter3MineralDeposits77 Geochemically Abundant and Scarce Metals 78 Ore Minerals 80 Native Metals 81 Sulfides 81 Oxides and Hydroxides 82 Carbonates and Silicates 82 ation of Mineral Deposits 82 Magmatic Concentration 83 Hydrothermal Solution 89 Metasomatic Replacement 97 Groundwater 98 Seawater or Lake Water 99 Rainwater 103 Flowing Surface Water 106 Alluvial Placers 107 Placer Deposits 108 Beach Placers 109 Metallogenic Provinces and Epochs 109 Chapter4TheSilicates111 Amphiboles 125 Chemical Composition 126 Crystal Structure 128 Physical Properties 131 Origin and Occurrence 133 Feldspars 135 Chemical Composition 136 Crystal Structure 139 Alkali Feldspars 142 172 158 Physical Properties 143 Origin and Occurrence 146 Uses 146 Feldspathoids 148 Chemical Composition and Crystal Structure 148 Physical Properties 149 Origin and Occurrence 150 Uses 151 Garnets 151 Chemical Composition 151 Crystal Structure 153 Physical Properties 154 Origin and Occurence 156 Uses 157 Jade 157 Olivines 161 Chemical Composition 162 Crystal Structure 163 Physical Properties 164 Crystal Habit and 165 Origin and Occurrence 166 Pyroxenes 171 Chemical Composition 173 Orthopyroxenes 175 Crystal Structure 176 Physical Properties 179 Origin and Occurrence 182 Zeolites 184 Chapter5MicasandClay Minerals187 Micas 187 Muscovite 188 Chemical Composition 189 Crystal Structure 189 181 200 32 237 197 Physical Properties 190 Origin and Occurrence 192 Uses 194 Clay Minerals 195 Structure 197 Clay 202 Differential Thermal Analysis DTA 209 Chemical and Physical Properties 214 Occurrence 221 Origin 224 Industrial Uses 226 Chapter6SilicaMinerals228 Physical and Chemical Properties 228 Origin and Occurrence 230 Solubility of Silica Minerals 230 The Silica Phase Diagram 232 Uses 232 Individual Silica Minerals 234 Quartz 234 Sard and Sardonyx 239 Chalcedony 239 Jasper, Chert, and Flint 240 High Quartz β-Quartz 242 Tridymite 243 Cristobalite 243 Opal 244 Vitreous Silica 244 Melanophlogite 245 Keatite 245 Coesite and Stishovite 245 Chapter7CarbonatesandOther Minerals247 The Carbonates 248 266 265 279 Aragonite 249 Calcite 249 Dolomite 257 Other Common Rock-ing Minerals 263 Magnetite and Chromite 264 Magnesite 265 Halite, Gypsum, and Anhydrite 265 Epidote 266 Hematite 267 Limonite 267 Other Mineral Groups 268 Arsenate Minerals 273 Halide Minerals 274 Nitrate and Iodate Minerals 277 Oxide Minerals 278 Chromate Minerals 289 Phosphate Minerals 290 Sulfate Minerals 296 V anadate Minerals 305 Sulfide Minerals 307 Sulfosalts 318 Molybdate and Tungstate Minerals 319 Conclusion 322 Glossary 323 Bibliography 326 Index 331 IntroductIon IntroductIon xi I f rock can be thought of as the foundation upon which all life on Earth stands, minerals are the foundation upon which rocks are built. Essentially, minerals are the most simple chemical compounds that make up rocks. This book is designed to take the reader on a tour of the various mineral groups, the unique characteristics that set one mineral apart from another, the features different groups of minerals share, and the roles minerals play in the rocks themselves. Each of the roughly 3,800 known mineral types has a unique chemical and physical structure. Such com- pounds may be relatively simple, as in a deposit of gold Ag, or they may be relatively complex combinations of several elements, as in the phosphate mineral tur- quoise CuAl6PO44OH ∙ 4H2O. Such combinations of chemical elements repeat throughout the mineral’s structure, and the mineral’s unique chemistry also drives a its internal physical structure. All minerals are solids and occur as crystals, and the ordered arrangements of repeating molecules generate the mineral’s crystal . Since the chemistry of each mineral is different, no two minerals can produce the same crystals. Thus, the shape of each mineral is unique, a feature useful for determining its identity. This unique crystal can change when temperature and pressure conditions change. Diamond and graphite, for example, are different s of the mineral carbon; however, dia- mond develops under high-temperature and high-pressure conditions. Minerals are typically thought of as inorganic sub- stances that in one of four ways. They can coalesce and crystallize in cooling magmas, solidify when bits and 7 Introduction 7 A mineral sample of wavellite. S xii 7 Minerals 7 pieces of sedimentary rock come together under condi- tions of increasing pressure, arise from older minerals that undergo metamorphoses, or precipitate from the action of magma mixing with seawater and groundwater. Despite their inorganic labelmeaning that they do not possess carbon-hydrogen bonds, which are characteristic of living tissuesliving things can produce minerals. Many car- bonate minerals originate as the shells of corals and other marine animals that died long ago. Such hard parts, which are made of calcite produced by these organisms, become calcite in rock after millions of years of increasing pressure and temperature. In addition, true minerals occur natu- rally. Although industrial processes can produce synthetic versions of diamonds, gemstones, and other minerals, their natural counterparts are the most prized. Since the study of minerals often takes place in remote locations, it is relatively difficult to determine the exact identity of a mineral observed in the field. Geologists are usually not equipped to per detailed chemical and physical analyses of minerals on the sides of moun- tains, in stream beds, and within rock outcroppings far from their laboratories. Instead, they rely on a battery of relatively simple tests to determine, or at least narrow down, the mineral they are looking at. The tests include an examination of several of the mineral’s physical proper- ties, including the mineral’s crystal habit shape and its relative hardness, how the mineral fractures, its specific gravity, its colour and luster, and the colour of streak it leaves on a porcelain streak plate. Other properties, such as the mineral’s attraction to magnets, fluorescence, reac- tion to hydrochloric acid, and radioactivity can also be determined in the field using tools the geologist can carry. Back in the laboratory, one of the most useful tools to determine a mineral’s identity is the petrographic micro- scope, which is designed to examine the minerals contained xiii in thinly sliced sections of rock. In addition, a compre- hensive battery of chemical tests, that consider how the mineral reacts to various acids and bases can be pered on the mineral in this setting. In some laboratories, X-rays can be used in a process called X-ray diffraction to deter- mine the identity of the mineral. As X-rays pass through the sample, they bounce off the various atoms and ions inside; this scattering produces a unique X-ray pattern that can be used to identify the mineral. Once the identity of the mineral is known, it can be placed into one of sev- eral large mineral groups. Rock-ing minerals that rocks are usually divided into five main groups. The overwhelming majority some 92 percent of all minerals in Earth’s crust occur in the silicate group, a division made up of minerals that con- tain different arrangements of silicon and oxygen atoms. These two abundant elements combine to silicon- oxygen tetrahedrons. Silicate tetrahedrons can appear alone to minerals such as olivine. They can also combine to single chains as in the mineral augite or double chains as in hornblende. Silica minerals can occur as sheets, as in micas and clay minerals, as well as complex structures called framework silicates to produce different types of quartz and feldspar. The other four main groups which are collectively called the non-silicates are made up of the carbon- ates, oxides, sulfides, and sulfates. Carbonate minerals are identified by their carbonate ions CO23 and occur widely across Earth’s surface. They dissolve relatively eas- ily in acids. Since water is a weak acid, carbonate deposits exposed to water are often the sites of caves, sinkholes, and similar lands. Oxides when metal and oxygen ions bond with one another. The ionic bonds between the positively charged metal ions and the negatively charged oxygen ions 7 Introduction 7 xiv are strong, and the oxide minerals that result are often hard and dense. Such minerals are routinely used to make steel and other metals. Hematite and magnetite are used to make iron, and chromite is the principal source of chro- mium from which steel alloys are made. Although ice does not contain metal ions, the positive charge of hydrogen bonds easily to the attractive negative charge in oxygen atoms, so it is also grouped with the oxides. Sulfides are similar to oxides in that they also bonds with metals; however, the bonds are not always ionic. Covalent bonds, in which electrons are shared between the atoms, and metallic bonds, in which clouds of electrons exist around densely packed positive ions, also occur. Galena which is an ore of lead and pyrite a mineral used to recover iron, nickel, and some precious metals are examples of sulfides. Sulfates, known by their characteristic sulfur group SO42-, are similar to silicates in that they tetrahe- drons in which a central ion is surrounded by four oxygen atoms. However, sulfates do not occur in chains and sheets. Its sulfur group, however, can bond with positive ions, such as calcium, to compounds such as gypsum which is the main component in sheetrock. Beyond the five main groups, there are several, smaller groups of minerals. Sulfosalts, compounds characterized by the presence of arsenic and antimony, give up sulfur to incorporate semimetals, such as arsenic and antimony, into their structures. In contrast, halide minerals contain large negatively charged ions, such as chlorine, bromine, iodine, and fluorine. A few of the smaller mineral groups, such as the nitrate, borate, and phosphate minerals have are similar to those discussed previously. Nitrate minerals parallel the carbonates; they have a nitrate group NO3- that functions like the carbonate group. Similarly, borate minerals, which contain linking boron-oxygen groups, 7 Minerals 7 xv parallel the silicates. Lastly, the construction of phos- phate minerals, known by their characteristic sulfur group PO43-, resembles that of the sulfates. Although most minerals are compounds of different chemical elements, some minerals are made up of only one. These solids, known as native elements, do not com- bine with others. Probably one of the best known native elements is gold Ag. Gold atoms bond with other gold atoms to a pure mineral unsullied by other chemical elements. Other metallic native elements include other valuable minerals such as silver, copper, and platinum. Native elements also occur as semimetals, such as arsenic and tellurium,which also appear in sulfosalts, and nonmet- als, such as carbon and sulfur. Although the identification and classification of minerals is a valuable rcise, one must remember that minerals are prized because of their ability to support or improve life. Through erosion and other natural forces, minerals are brought to Earth’s surface over time. Some minerals, such as a number of phosphates and nitrates, serve as plant nutrients, and thus help to fuel a wide variety of living things and the ecosystems they inhabit. Others, however, are precious to humans because of their beauty and rareness or because they can be used to build better machines or serve as materials in building construction. Since most valuable minerals are locked up in rocks that contain other minerals that have little or no value, it may be useful to know how minerals are physically separated from one another. Mineral separation, or processing, is an activity that requires several steps. After the minerals in the rock are analyzed to determine their identity and concentration, they go through a two-step process called communition to free them from the rocks they occur in. In the first step, large pieces of rock are crushed down into manageable