ELEMENTS OF OPTICAL MINERALOGY AN INTRODUCTION TO MICROSCOPIC PETROGRAPHY BY ALEXANDER N. WINCHELL, Doct. Univ. Paris Professor of Mineralogy and Petrology , University of Wisconsin SECOND EDITION, SECOND PRINTING PART III. DETERMINATIVE TABLES WITH A COLORED CHART AND Two DIAGRAMS NEW YORK JOHN WILEY SONS, INC. LONDON CHAPMAN HALL, LIMITED 939 COPYRIGHT, 1929, 1939 BY ALEXANDER N. WINCHELL All Rights Reserved This book or any part thereof must not be reproduced in any form without the written permission of the publisher. PRINTED IN U. 8. A. PRESS OF BRAUNWORTH A CO., INC. BUILDERS OF BOOKS BRIDGEPORT. CONN. PREFACE TO THE SECOND EDITION SECOND PRINTING DURING the ten years since the publication of the second edition of these tables many new minerals have been described. About fifty of these are included in the third edition of Part II, which was published in 1933, while nearly seventy are of more recent date. The author has attempted to include in supplementary tables in this printing all the new minerals which seem to be well established and adequately described as to their optical properties. Unfortunately it has not been feasible to incorporate them in the main tables, but this is probably not a very serious difficulty since the minerals in question are all very rare. It is hoped that the use of colored paper for the table III classify ing minerals on the basis of their color and pleochroism in thin section will make it easy to find the various tables quickly and con veniently. In the preparation of this printing the author has benefited by the assistance and encouragement of his wife, Florence S. Winchell. ALEXANDER N. WINCHELL MADISON, WISCONSIN March, 1939 PREFACE TO THE SECOND EDITION Or course tables prepared for the determination of minerals by optical methods should be based on the chief optical properties of the minerals. However, it is not at all obvious just which optical prop erty should be used first in classifying the minerals. After several attempts to combine the most important properties in one table so that more than one of them could be used first, it seemed wiser to simplify the arrangement by making separate tables for each important property. In addition to the tables which are given, tables might be prepared based primarily upon the optic angle, optic sign, or extinction angles. However, the practical groups based upon optic angle or optic sign are too few in number to be satisfactory, while extinction angles are almost useless in distinguishing between tetragonal, hexagonal and orthorhombic minerals. Thus it comes about that the chief tables which are given are based upon refringence, or birefringence, or color and pleochroism. As the dispersion methods of determining minerals come into wider use the table based upon dispersion will become more complete and more useful. It is a pleasure to acknowledge that these tables have been improved as a result of thoughtful constructive criticism of the first draft by Professor F. F. Grout of the University of Minnesota the writer has also had the advantage of an opportunity to examine copies of determinative mineral tables prepared by Professor Grout and others prepared by Professor D. J. Fisher of the University of Chicago. He has also benefited notably by frequent consultations with Professor R. C. Emmons of the University of Wisconsin. Plate II, based on refringence and birefringence, has been prepared along lines suggested by Professor C. O. Swanson of the Michigan College of Mines and Professor R. H. B. Jones of the State College of Washington. ALEXANDER N. WINCHELL. MADISON, WISCONSIN, January, 1929 vu CONTENTS PAGE INTRODUCTION i TABLE I. OPAQUE MINERALS 7 TABLE II. BIREFRINGENCE OF MINERALS 10 SUPPLEMENTARY TABLE II. BIREFRINGENCE OF MINERALS 76 TABLE III. COLOR OF MINERALS go SUPPLEMENTARY TABLE III. COLOR OF MINERALS 130 TABLE IVA. REFRINGENCE OF ISOTROPIC MINERALS 136 SUPPLEMENTARY TABLE IVA. REFRINGENCE OF ISOTROPIC MINERALS 141 TABLE IVB...