A HANDBOOK OF MINERALS,CRYSTALS,ROCKS AND ORES
authored by: P.O. Alexander
Hardback
Buy from FlipkarteChapter
The book is divided into four sections, minerals, crystals, rocks and ores. Section A incorporates nine s, begins with presenting salient features of the earth--its structure and composition. The second Minerals and Mineralogy briefly tells about their diversity and their categorisation and introduces the interesting way they are named. Crystal chemistry the third is the heart and soul of mineralogy and deals in somewhat details about the building blocks of minerals -atoms and ions and the way they form diverse types of minerals are. It tries to tell why every combination of chemical compounds cannot result into a naturally occurring mineral. The fourth and fifth s deal with Properties of Minerals, physical and optical. The s describe various physical properties that are helpful in the identification both in hand specimens and as thin section under the microscope. These two s are adequately aided with a number of illustrations, photographs and photomicrographs to bring home the point. five deals with classification of minerals and their occurrence and forms a prelude to the next two s on descriptive mineralogy. Important silicate and non silicate minerals are described in s eight and nine. A brief description of mineral uses is dealt with in both descriptive mineralogy as well Section D on mineral deposits, however, the last , Mineral uses presents an overall picture and will be interesting as well as educating to students and even general readeSection B is devoted to crystals and crystallography. one introduces the subject while two presents basic crystallographic elements. three deals with the main six crystals systems while also giving a preliminary idea about stereographic projection and x-ray crystallography. Section C covers petrology, beginning with introduction to science of petrology, rock nomenclature. two is devoted to the study of igneous rocks, including their forms, composition, textures, structures, classification and description. Sedimentary rocks is the theme of three while different aspects of metamorphic rocks including kinds and agents of metamorphism and classification and description of metamorphism. The last portion of this also considers metamorphism in the background of global tectonics. five, the rock cycle presents a concise summary of geological events that have shaped the planet earth. The last section D is what geology is all about for a man on the street and its significance in nation building--the Ore minerals. It begins with what ore is and its place in human affairs as a well as presenting the important terminology in economic geology. two deals with ore genesis and presents various hypogene and supergene process that carves out ore deposits from non economic materials. three, mineral deposits and global tectonics is becoming a very popular theme among the earth scientists. A brief introduction of the same will be certainly appreciated by the student community and prompt them for further study in this direction. A general survey of India's mineral resources is the theme of four. It covers almost all of the commonly used ores, metallic, non metallic or fuels. The last of section D and the boom, 'Indian mineral industry: some facts and figures' will present where our country stands in the realm of mineral resources. Latest available data of resources, production, export, import, organisations that matter and other useful facts and figures are presented.
Pramod O Alexander: Prof. (Retd.) of Geochemistry, Department of Applied Geology, Dr. H.S. Gour University, (Formerly University of Saugar), Sagar, Madhya Pradesh, India
Foreword
Preface
Acknowledgement
Section A: Minerals
Chapter 1 The Earth
Salient Features; Crust Mantle and Core
Chapter 2 Minerals and Mineralogy
Minerals and Minerals; Different Categories of Minerals; Naming of Minerals
Chapter 3 Elements of Crystal Chemistry
The Solid State; Atoms, Ions, Ionic-size, Ionic-charge, Coordination Number; The Design in Metals; Bonding in Minerals; The Ionic Bond; The Covalent Bond; The Metallic Bond; van der Walls’ Bond; Summary; The Silicate Structures; Isomorphism; Atomic Substitution and Atomic Substitution;Polymorphism; Breaking apart a Crystal Lattice
Chapter 4 Physical Properties of Minerals
Characters depending on Light, Colour; Transparency; Lustre; Characters depending on State of Aggregation, Specific Gravity; Form; Habit; Cleavage; Parting; Fracture; Hardness; Tenacity; Pseudomorphism and Polymorphism; Characters depending on Senses, Feel, Odour, Taste; Characters depending upon-Heat, Magnetism, Electricity and Radioactivity; Properties under darkness; Macroscopic identification of Minerals: Few Examples; Self Assesment Questions
Chapter 5 Optical Properties of Minerals
Light; Refractive Index; The Petrological Microscope; Plane Polarised Light; Double Refraction; Uniaxial +ve and –ve Minerals, The Nicol Prism; Preparation of Thin Section; Microscopic Adjustments, Illumination, The Nicol Position; Vibration Direction of Polarisor; Centring the Objective; Mineral under the Microscope; Properties under Ordinary Light- Colour; Transparency, Relief; Cleavage; Inclusion; Alteration; Properies under P.P.L. Pleochroism; Pleochroic Haloes; Twinkling; Isotropic & Anisotropic Minerals Under Crossed Nicols; Isotropic Minerals; Anisotropic Minerals; Polarisation Colours; The reason behind Polarisation Colours; Phase Difference, Retardation and Birefringence; Phase Difference, Order of Colours & the Quartz Wedge; Determining the order of Polarisation Colours; Gypsum & Mica Plate; Polarisation Colours and the Extinction Position; Extinction and Extinction Angle; Types of Extinction; Other Properties-Twinning; Zoning; Elongation; Alteration; Mineral Under Microscope- Garnet; Olivine, Hornblend; Plagioclase; Studies under Convergent Light; The Optical Indicatrix; Interference Figures; Uniaxial Minerals, Biaxial Minerals; Preliminary ideas on Reflected Light Microscopy
Chapter 6 Minerals: Their Classification and Occurrence
Classification; The Occurrence of Minerals; Common Mineral of Igneous Rocks; Common Minerals of Sedimentary Rocks; Common Minerals of Metamorphic Rocks; Minerals of Pegmatites; Minerals and Ore Deposits
Chapter 7 The Silicate Minerals
Silicate & Non-Silicate Minerals; The Silicate Minerals; Olivine; Pyroxenes; Amphiboles; Pyroxenes and Amphiboles, Similarities & Differences; Micas; Felspars, Potash Felspars, Plagioclase Felspars; Felspathoids; Zeolites; Pegmatites and Accessory Minerals, Tourmaline, Topaz, Beryl, Sphene, Zirion; Common Metamorphic Minerals, Garnets; Alumino Silicates, Kyanite, Andalusite, Sillimanite, Staurolite; The Green Group; The White & Grey Minerals, Minerals; Pyroxenoids; Other common Metamorphic Minerals
Chapter 8 The Non-Silicate Minerals
Metals; Non Metals; Sulphides; Phosphates; Carbonates; Haloids; Oxides; Common Sedimentary Minerals, Carbonates; Sedimentary Oxides and Hydroxides; Sulphates; The Clay Minerals; Special Weathering product, Bauxite; Gem Stones
Chapter 9 Mineral Uses
Introduction, Two Mineral Innumerable Uses; Abrasives, Adsorbents, Building Stones and Road metal; Cement, Ceramics and Glass, Chemicals; Cosmetics, Decorative and Ornamental Stones, Drilling and Cutting, Dyeing and Pigments, Insulators; Electronics, Fertilisers, Insecticides and Pesticides, Fillers, Extenders and Dilutants; Flux, Food Industry, Foundry, Fuels; Gemstones and Jewellery; International Monetary Settlement, Medicinal, Metals and Alloys; Nuclear Applications; Optics, Paints, Primers, Lubricants and Plastics, Petroleum/Gas Refining, Pyro and Piezoelectrics; Refractory, Rubber and Leather, Scientific Equipments, Miscellaneous; Per Capita Consumption of Minerals
Section B: Crystals
Chapter 1 Introduction
Introduction; Minerals as Crystals; Brief Historical Background; Mineral Kingdom into Six Systems; Some fundamental Definitions
Chapter 2 Elements of Crystallography
Morphological Elements; Faces, Edges, and Soild Angle; Symmetry Elements; Plane of Symmetry; Axes of Symmetry; Centre of Symmetry; Axial Length and Axial Ratios; Indexing a Face; Parameters and Indices; Notation of Crystal Faces; Parameter System of Weiss; Miller’s Index System; Open and Closed Forms
Chapter 3 The Six Crystal Systems
Introduction; Cubic or Isometric System; Galena Type; Forms, a general statement; Etch Figures and Solution Pits; Galena Type Forms; Combinations in Galena Type; Common Galena Type Minerals; Pyrite Type, Forms; Pyritohedron and Diploid; Common Minerals; Tetrahedrite Type; Common Minerals; Hemihedrism; Tetragonal System; Symmetry Elements; Forms; Common Zircon Type Minerals; Orthorhombic System; Symmetry Elements; Forms; Common Baryte Type Minerals; Monoclinic System; Symmetry Elements; Forms; Common Minerals; Triclinic System; Symmetry Elements; Forms; Common Minerals; Hexagonal and Trigonal Systems; Hexagonal System; Beryl Type; Symmetry Elements; Forms; Common Minerals; Trigonal System; Calcite Type; Symmetry Elements; Forms; Common Minerals; Tourmaline Type; Symmetry Elements; Forms; Common Minerals; Quartz Type; Symmetry Elements; Forms; Symmetry Elements; Twinning, Twin Plane; Twin Axis; Composition Plane and the Twin Laws; Recognising Twins; Types of Twins; Twinning in Six Systems; Has Twinning some uses?
Chapter 4 Preliminary Ideas on Stereographic Projection and X-ray Crystallography
Introduction; Stereographic Projection; Stereographic Net; X-ray Crystallography
Section C Rocks
Chapter 1 Introduction
Petrology; Petrography and Petrogenesis; Rocks as storehouses of Minerals; The Three Groups of Rocks
Chapter 2 Igneous Rocks
Introduction; Intrusive Rocks; Forms of Intrusive Rocks; Batholith; Stock; Laccolith; Lopolith; Phacolith; Sill, Dykes; Veins and Reef; Extrusive Rocks; Plateau Basalts; Volcanic Mountains; Volcanic Craters; Calderas; Pyroclastics; Textures and Structures of Igneous Rocks; Textural Elements; Grain Size; Shape of the Mineral Grains; Texture Types; Granular; Porphyritic and Intergrowth; Miscellaneous Textures; Common Structures; Classification of Igneous Rocks; Introduction; Field Classification; Textural Classification; Colour Criteria; CIPW Classification; Mineralogical classification; IUGS Classification; Chemical Classification; Variation Diagrams; Description of Igneous Rocks; Ultrabasic Rocks; Perdotites; Dunite; Pyroxenites; Hornblendite; Volcanic Ultrabasites; Komatite; Kimberlites; Basic Rocks; Gabbro; Anorthosites; Basalt; Lunar Basalt; Dolerite; Intermediate Rocks; Diorites; Andesites; Intermediate Rocks with K- Felspar; Syenites; Trachytes; Acid Rocks; Granites; The Granite Family; Vein Rocks; Acid Volcanics; Alkaline Rocks; Some peculiar Igneous Rocks; Lampropyres; Carbonatites; Ophiolites
Chapter 3 Sedimentary Rocks
Introduction; Sediments and Sedimentary Rocks; Broad Categories of Sediments; Factors affecting Sedimentary Process; The sequence of breakdown; Primary and Secondary Minerals; Mineralogy of Sedimentary Rocks; Mineralogical Maturity; Depositional Environments; Classification of Sediments and Sedimentary Rocks; Textures of Sedimentary Rocks; Sedimentary Structures; Depositional Sedimentary Structures; Erosional Sedimentary Structures; Secondary Sedimentary Structures; Miscellaneous Sedimentary Structures; Biogenic Structures; Description of Sedimentary Rocks; Rudaceous Rocks; Conglomerates; Breccias; Agglomerate; Volcanic Ash; Arenaceous Rocks; Sandstone; Graywackes; Arkose, Grit; Orthoquartzite; Matrix and Cement; Argillaceous Rocks; Shale; Mudstone; Claystone; Orthochemical and Allochemical Rocks; Chemically Precipitated; Clastic/Detrital; Organic Limestones; Dolomites and Dolomitisation; Other Chemically Precipitated Rocks; Chert; Evaporites; Phosphates; Carbonaceous Rocks; Sedimentary Rocks and Natural Resources
Chapter 4 Metamorphic Rocks
Metamorphism and Metasomatism; Agents of Metamorphism; Types of Memorphism; Thermal Metamorphism; Dynamic Metamorphism; Regional Metamorphism; Polymetamnorphism; Retrograde Metamorphism; Autometamorphism; Shock Metamorphism; Ultramtamorphism; Metamorphic Minerals; Naming Metamorphic Rocks; Grade of Metamorphism; Metamorphic Zones and Index Minerals; Metamorphic Facies; The Original eight Facies of Eskola; Newly Introduced Facies; Textures and structures of Metamorphic Rocks; Textures; Igneous & Metamorphic; Important Texture types; Description of Metamorphic Rocks; Contact and Regional Metamorphic Rocks; Hornfels, Slates; Phyllites; Schists; Gneisses; Granulites; Eclogites; Quartzites; Marble; Amphibolites; Migmatites; Rocks formed by Dislocation Metamorphism: Crushed; Breccias; Cataclasstics; Mylonites; Phyllonites; Triangular Plots in Metamorphic Petrology; ACF Diagram; AKF Diagram; AFM Diagram; Metamorphism & Global Tectonics; Burial Metamorphism Regional Metamorphism in Orogenic Belts; Blue Schist Metamorphic Belts; Twinned Metamprphic Belts; Metamorphism Along Transform Faults
Chapter 5 The Rock Cycle
Introduction; Involvement of Energy in the Rock Cycle; The Rock Cycle and Mineral Deposits
Section D: Ores
Chapter 1 Ore Minerals
Introduction; Ores; Ore Minerals and Economic Deposits; Minerals in Human Affairs; Ore Minerals Against the Background of Average Crustal Composition; Important Terminology in Economic Geology
Chapter 2 Genesis of Ore Deposits
Introduction; Present Classification; Deposits formed Due to Internal Processes; Magmatic Concentration Deposits; Magmatic Deposits and Rock Associations; Contact Metasomatic Deposits; Some Important Contact Metasomatic Deposits of the World; Hydrothermal Ore Deposits; Cavity Filling and Replacement; Resulting Deposits; Different Types of Cavity Filling; Cavity Filled Deposits; Metasomatic Replacement Deposits; Dissiminated Type; Replacement Lode Type; Criteria of Replacement; Significance of Hydrothermal Alterations; Sericitization; Dolomitization; Silicification; Argillic Alteration; Prophylitic Alteration; Summary; Stable Isotopic Studies; Ore Shoots; What is so Special About Porphyry Copper Deposits ? Pegmatite Deposits; Simple and Complex Pegmatites; Zoning in Complex Pegmatites; Sublimates; Metamorphic Deposits; Graphite; Kyanite; Andalusite; Sillimanite; Asbestos; Talc Steatite; Serpentine; Pyrophlllite; Metamorphosed Deposits; Banded Iron Formations; Manganese Deposits; Mineral Deposits formed by Surface Processes; Placer Deposits; Elluvial; Colluvial; Aeolin. Beach; Fossil; Residual Deposits; Residual Aluminium Deposits; Residual Nickel Deposits; Supergene Enrichment Deposits; Anatomy of Supergene Deposit; Chemistry Involved; Gossans or Iron Hat; Chemical Precipitates; Banded Iron Formations (BIF); BIF of Lake superior Area; Phanerozic Iron Ores; Oolites; Sedimentary Manganese Deposits; Volcanogenic Sedimentary Deposits; Non-Volcanogenic Sedimentary Deposits; Separation of Fe and Mn an Enigma; Manganese Nodules; Sedimentary Cu-Pb. Zn Deposits; Stratiform and Stratabound Deposits; Phosphorites; Origin of Phosphorites; Lithoassociation and Phosphorites; Modern Phosphatic Deposits; Evaporite Deposits; Order of Salt Deposition; Types of Deposits; Sabkhas; Microbial Ore Deposition; Metallogenic Provonce and Epoch; Metallogenic Epoch: Indian Scenario; Summary of Standard Classification of Ore Deposits; Some Indian Examples of Classical Ore Types; Energy Resources: Coal and Petroleum; Introduction; Coal; Coal Components; Chemical Composition of Coal; Origin of Coal; Environment and Age of Coal Formation; Age and Distribution; Coal Classification; Rank of Coal; Peat; Lignite; Bituminous Coal; Anthracite; Coal Lithotypes; Coal Macerals; Black Diamond has Its Uses; Oil from Coal; Petroleum; Brief Historical Background; Composition; Rare Elements; Origin of Petroleum; Organic Origin; Migration; Reservoir; Cap-rocks and Traps; Other Fossil Fuels; Oil Shales; Tar Sands
Chapter 3 Mineral Deposits and Global Tectonics
Introduction; Constructive Boundaries; Destructive Boundaries; Conservative Boundaries; Ore Deposits and Plate Tectonics; Ore Deposits at Constructive Margins; Ore Deposition at the Destructive Boundary; Mantle Plume; Hot Spots and Ore Deposits; Ore Deposits and Continental Rifting; Petroleum; Salt Deposits and Plate Movements; Ore Deposits in Cratonic Areas; Plate Tectonics and Mineral Exploration
Chapter 4 Indian Mineral Deposits
Introduction; An Applied Classification of Mineral Deposits; Commonly Used Terms; Mineral Occureence; Ore Reserves and Mineral Resources; United Nations Framework Classification (UNFC); Iron, Manganese; Chromium; Nickel & Cobalt; Titanium; Tin; Vanadium; Tungsten; Aluminium; Copper; Lead & Zinc; Precious Metals-Gold; Silver; Platinum; Fertiliser Minerals-Apatite; Phposphorite; Gypsum; Sulphur & Pyrite; Barytes; Limestone and Dolomites; Marble; Wollastonite; The Alumino Silicates-Kyanite; Sillimanite and Andalusite; Clays; Insulators-Mica; Asbestos; Vermiculite; Magnesite; Silica Minerals; Talc; Soapstone; Steatite; Diamond and Gem Stones; Graphite; Minor Minerals; Granite; Slate; Sandstone and Other Dimension Stones; Bentonite and Fuller’s Earth; Salt; Other Minor Minerals; Fuels; Coal; Lignite; Petroleum and Natural Gas; Gas Hydrate-Fuel for Future; Coal Bed Methane Potential; Uranium; Thorium; Rare Earth & Rare Metals; Last but not the Least-Groundwater; Introduction; Groundwater, the hidden Mineral Resource; Summary of Groundwater Scenario in India; Groundwater Reserves; Searching for water; Geological Methods; Geophysical Methods; Depletion Faster than Recharge
Chapter 5 Indian Mineral Industry: Some Facts and Figures
Introduction; Resource Position; Production; Prices; Foreign Trade; Premier Geological Organisations; The Future is Bright
Colour Plate Section
Appendix
1. India’s Mineral Reserves and Resources
2. Objective Type Questions Answers - Section A, B, C and D
Bibliography
References
Index
Preface The title “A Handbook of Minerals, Crystals, Rocks and Ores” took shape in my mind towards the last stages of my teaching and research career, spanning over thirty eight years. I am still at it voluntarily. The book writing project of the Department of Science & Technology for retired scientists made the platform to work on within a time frame, which otherwise might have taken much longer. Inspiration and motivation, however came from a large number of my former students who seem have benefited through my teaching (so they say). There are very few themes which are ‘new’. Most of the matter has been said or written earlier by celebrated authors. In the present text, the only difference may be some new concepts and data (that has emerged in recent years) and the way it is presented. The book has been written in a style and language which will be easily understood even by those who don’t feel at ease in going through some of the excellent books by foreign authors. I have tried to concentrate on the most essentials and be concise, precise and as far as possible up-to date with facts and figures. The emphasis has been to create interest and desire to study further. Indeed, I have tried to present a volume which I would have appreciated as a student during my times. The book covers the prescribed syllabus for the undergraduate courses in mineralogy-crystallography, igneous petrology and economic geology by the University Grants Commission (UGC), New Delhi. The section on ores, is fairly exhaustive and will equally serve the post-graduate students for their economic geology papers. The book has the relative advantage of incorporating recent concepts in earth sciences, in particular in the field of global tectonics as also for presenting up to date facts and figures for Indian Mineral Industry scenario. It will also serve as a ready reckoner to students appearing in various competitive examinations and facing interview boards. Besides, for professional geologists it will serve as a ready reference point. Civil Engineering students and entrepreneurs in mineral industry will also find this book useful. Lastly, the book will definitely be of help to young college and university teachers-especially to those who are teaching under-graduate classes. The book is divided into four sections, minerals, crystals, rocks and ores. Section A incorporates nine chapters, begins with presenting salient features of the earth- its structure and composition. The Second chapter Minerals and Mineralogy briefly tells about their diversity and their categorisation and introduces the interesting way they are named. Crystal Chemistry the third chapter is the heart and soul of mineralogy and deals in somewhat details about the building blocks of minerals- atoms and ions and the way they form diverse types of minerals are. It tries to tell why every combination of chemical compounds cannot result into a naturally occurring mineral. The fourth and fifth chapters deal with Properties of Minerals, physical and optical. The chapters describe various physical properties that are helpful in the identification both in hand specimens and as thin section under the microscope. These two chapters are adequately aided with a number of illustrations, photographs and photomicrographs to bring home the point. Chapter five deals with classification of minerals and their occurrence and forms a prelude to the next two chapters on descriptive mineralogy. Important silicate and non silicate minerals are described in chapters eight and nine. A brief description of mineral uses is dealt with in both descriptive mineralogy as well Section D on mineral deposits, however, the last chapter, Mineral uses presents an overall picture and will be interesting as well as educating to students and even general readers. Section B is devoted to crystals and crystallography. Chapter one introduces the subject while chapter two presents basic crystallographic elements. Chapter three deals with the main six crystals systems while also giving a preliminary idea about stereographic projection and x-ray crystallography. Section C covers petrology, beginning with introduction to science of petrology, rock nomenclature. Chapter two is devoted to the study of igneous rocks, including their forms, composition, textures, structures, classification and description. Sedimentary rocks is the theme of chapter three while different aspects of metamorphic rocks including kinds and agents of metamorphism and classification and description of metamorphism. The last portion of this chapter also considers metamorphism in the background of global tectonics. Chapter five, the rock cycle presents a concise summary of geological events that have shaped the planet earth. The last section D is what geology is all about for a man on the street and its significance in nation building – the Ore Minerals. It begins with what ore is and its place in human affairs as a well as presenting the important terminology in economic geology. Chapter two deals with ore genesis and presents various hypogene and supergene process that carve out ore deposits from non economic materials. Chapter three, mineral deposits and global tectonics is becoming a very popular theme among the earth scientists. A brief introduction of the same will be certainly appreciated by the student community and prompt them for further study in this direction. A general survey of India’s Mineral resources is the theme of chapter four. It covers almost all of the commonly used ores, metallic, non metallic or fuels. The last chapter of Section D and the book, ‘Indian Mineral Industry: some facts and figures’ will present where our country stands in the realm of mineral resources. Latest available data of resources, production, export, import, organisations that matter and other useful facts and figures are presented which I am sure will be helpful to not only a student of geology but to any one interested in India and its mineral resources. The book is presented to the student community with the hope that it will be useful to them. Comments and suggestions from them will be appreciated and help to improve it, should a revised edition comes in future. During the course of writing this book I have relearned the fact that there is no end to learning and there is a limit to human perfection. The purpose of writing this text will be more than fulfilled if its helps the reader to create interest not only in the mineral kingdom but develops a lifelong passion for learning.
Minerals are the building blocks of the earth’s crust. Derived inorganically, either as chemical elements or more often as chemical compounds, minerals are essentially solid. Minerals often form crystals, while aggregate of minerals constitute a rock. Mineralogy is the discipline devoted to the study of minerals including their formation, occurrence, properties, composition and classification . Needless to say, the subject of mineralogy is the foundation of crystallography, petrology and other branches of geology. Section A dealing with Minerals comprises nine chapters. Chapter I presents salient features of the earth including composition. and structure of the crust mantle and core. Chapter II presents their categories and the how minerals derive their names. Since minerals are essentially a combination of atoms and molecules the significance of chapter III which deals with crystal chemistry cannot be over emphasized.. Chapter IV and V deal with physical and optical properties of minerals which are crucial in identifying them in hand specimens and under the polarising microscope. Classification of minerals and their occurrence is dealt in a general way in chapter VI while descriptive mineralogy is presented in Chapters VII ( Silicate Mnerals) and VIII ( Non-Silicate Mnerals). Minerals are no doubt a subject of serious scientific curiosity but ultimately their use to man is by far the most important theme. Chapter IX therefore is devoted exclusively to different uses that are minerals are put to. The chapter ends with eye opening information as to the quantum of minerals that man uses, taking one of the most industrialized nation USA as an example.
The Mineral Kingdom presents a dazzling floral-display in the form of natural crystals. This is what makes mineralogy a very fascinating subject both for an amateur as well as an expert. Unless one visits the celebrated Lechuguilla cave in New Mexcio, USA it will be difficult to visualize the breathtaking beauty that crystals present. This, over 160 km cave is lined with gigantic as well as delicate gypsum crystals- as thin as human hair to several centimetres across and 6 m long . Crystals come in all shapes, sizes and colours. Their beauty and regular shape has not only attracted the scientists but made them objects of magical and mythical powers in many cultures of the world. The study of crystals - including their growth, structure, classification by form and their physical properties forms the subject of crystallography. As of today one can’t think of this subject without x-ray crystallography, however, this being not in your syllabus only an introduction will be presented in the last chapter, while the entire section will be devoted to fundamental aspects of crystal morphology. The section comprises four chapters. Chapter I describes and introduces the theme, presents a brief historical background of the development of the subject and gives some fundamental definitions. Chapter II presents the morphological elements including symmetry elements( plane, axes and centre of symmetry), parameters, indices, notation of crystal faces and other related aspects which are the basis for dividing crystals of all shapes and sorts into six or seven systems and several sub-types. This chapter will help you understand as to why mineral galena belongs to cubic system, while gypsum is monoclinic, or as to why an octahedron is represented by a symbol (111) but a cube with (100). Chapter III describes the seven systems and their sub-types and ends with an account of twinning- a curious feature quite often encountered among crystals. The section ends with a preliminary idea about stereographic projection and x-ray crystallography.
A rock is the home for minerals. In other words, naturally occurring coherent aggregate of minerals (or glassy mass) will constitute a rock. Like in a family, more often, there are several members(minerals) within a rock but occasionally just one mineral also makes a rock( olivine in dunite, quartz in quartzite and calcite in marble). The root word petros is of Greek origin, meaning rock and a petrologist is one who specializes in the study of rocks. The three main categories of rocks are distinguished on the basis of their origin. Igneous rocks are the ones that have solidified from a molten state in deep seated conditions, as also on the surface while Sedimentary rocks are formed from the erosion of preexisting rocks and subsequent re-deposition or precipitation of the resulting material at or near the surface. Metamorphic rocks on the other hand, are formed by the action of heat or pressure or both on preexisting rocks. The theme of rocks is split into five chapters. The first chapter introduces the theme of petrology, petrography and petrogenesis., presents rocks as the storehouses of minerals and their grouping into three classes. The second chapter presents all the important aspects of igneous rocks( plutonic, hypabasal and volcanic) including their forms, texture, structure, chemistry and classification and variation diagrams. It also presents a somewhat sufficient description of different kinds of igneous rocks under the categories of ultrabasic, basic, intermediate acid and alkalic rocks. The chapter ends with an introduction to some of the peculiar kinds of igneous rocks and also presents a brief account of causes of diversity among igneous rocks. Chapter III is devoted to the study of sedimentary rocks beginning with nature and categories of sediments and general factors that affect sedimentary process. Sequence of breakdown, sedimentary minerals, depositional environment , classification of sediments and sedimentary rocks is the next theme followed by primary and secondary and biogenic structures. The next theme is a description of important sedimentary rocks under different categories ( rudaceous, arenaceous, asrgillaceous and rocks of biogenic origin). The chapter ends with introducing sedimentary rocks as the home for natural resources. Chapter IV dwells on metamorphic rocks distinguishing between metamorphism and metasomatism. Metamorphic minerals and naming metamorphic rocks is the next theme. Next, agents and types of metamorphism is followed by grade, zones, index minerals and metamorphic facies. Textures, structures and the description of metamorphic rocks comes next. The use of triangular plots in metamorphic petrology is introduced and ends with considering metamorphic process in the light of global tectonics. The last chapter is a short but important chapter- The Rock Cycle which combines the three important geo-processes of igneous activity, sedimentary process and metamorphism while presenting a birds eye view of them. It considers the movement, not only of matter but also the energy that drives the rock cycle. The chapter closes with introducing the rock-cycle-mineral deposits relationship.
As milk to a cow or fruit to a tree, ore is to Earth Sciences. Different academic and scientific aspects of geology are of no consequence to a common man. Ores and ore minerals from which valuable constituents could be extracted profitably is what the world is after- be it the continental masses, oceanic depths, desolate icy Antarctic tracts or now, even other planets of the solar system. The subject of economic geology is thus a subject of greatest interest among other natural sciences. This last section will dwell on the theme of metallic and non metallic ore deposits. The first chapter begins with fundamental definitions, signifying the importance of minerals in human affairs. It also looks at ore minerals against the background of average crustal composition and presents a glossary of important terms in economic geology. The second chapter is a lengthy chapter devoted to the ways ore deposits are formed ( ore genesis). Broadly, the processes are described under two categories, the internal processes and the surface processes. Fuel minerals are taken separately towards the end of this chapter. Chapter III briefly introduces the relationship between location of minerals deposits to the revolutionary theme of global tectonics which attempts to answer why a mineral deposits occurs where it occurs. The fourth chapter is devoted entirely to the Indian Mineral Deposits. It begins with a few important themes of mineral economics and dwells on the description of important Indian Mineral Deposits as to their geology, geography and economic potential. Lastly, the fifth chapter exclusively deals with the facts and figures of the Indian Mineral Industry presenting recent available data of resources, production, import, export and future prospects. It also gives a brief introduction to the important geo-scientific organizations of the country.
Colour Plate Section
minerals, crystals, rocks, ores, mineralogy, crystal chemistry, properties, classification, petrology, igneous rocks, sedimentary rocks, metamorphic rocks, ore minerals, economic geology, mineral deposits, global tectonics, india's mineral resources, mineral industry