Produced by Kevin Handy, Barbara Kosker, John Hagerson, Chrome and the Online Distributed Proofreading Team at http://www.pgdp.net THE ECONOMIC ASPECTS OF GEOLOGY C. K. LEITH UNIVERSITY OF WISCONSIN [Illustration] NEW YORK HENRY HOLT AND COMPANY COPYRIGHT, 1921 BY HENRY HOLT AND COMPANY _August, 1923_ PRINTED IN THE U. S. A. CONTENTS PAGE CHAPTER I. INTRODUCTION 1 SURVEY OF FIELD 1 ECONOMIC APPLICATIONS OF THE SEVERAL BRANCHES OF GEOLOGY AND OF OTHER SCIENCES 3 Mineralogy and petrology 3 Stratigraphy and paleontology 4 Structural geology 5 Physiography 6 Rock alterations or metamorphism 10 Application of other sciences 10 TREATMENT OF THE SUBJECT IN THIS VOLUME 11 CHAPTER II. THE COMMON ELEMENTS, MINERALS, AND ROCKS OF THE EARTH AND THEIR ORIGINS 13 RELATIVE ABUNDANCE OF THE PRINCIPAL ELEMENTS OF THE LITHOSPHERE 13 RELATIVE ABUNDANCE OF THE PRINCIPAL MINERALS OF THE LITHOSPHERE 14 RELATIVE ABUNDANCE OF THE PRINCIPAL ROCKS OF THE LITHOSPHERE 16 WATER (HYDROSPHERE) 18 SOILS AND CLAYS 18 COMPARISON OF LISTS OF MOST ABUNDANT ROCKS AND MINERALS WITH COMMERCIAL ROCKS AND MINERALS 18 THE ORIGIN OF COMMON ROCKS AND MINERALS 18 Igneous processes 19 Igneous after-effects 19 Weathering of igneous rocks and veins 20 Sedimentary processes 22 Weathering of sedimentary rocks 23 Consolidation, cementation, and other sub-surface alterations of rocks 24 Cementation 24 Dynamic and contact metamorphism 25 THE METAMORPHIC CYCLE AS AN AID IN STUDYING MINERAL DEPOSITS 27 CHAPTER III. SOME SALIENT FEATURES OF THE GEOLOGY AND CLASSIFICATION OF MINERAL DEPOSITS 29 VARIOUS METHODS OF CLASSIFICATION 29