MINERALS IN ROCK SECTIONS THE PRACTICAL METHODS OF IDENTIFYING MINERALS IN ROCK SECTIONS WITH THE MICROSCOPE ESPECIALLY ARRANGED FOR STUDENTS IN TECHNICAL AND SCIENTIFIC SCHOOLS BY LEA McILVAINE LUQUER, C.E., PH.D. _Late Assistant Professor of Mineralogy, Columbia University, New York City_ _FOURTH REVISED EDITION_ [Illustration: [Logo]] NEW YORK D. VAN NOSTRAND COMPANY, INC. 250 FOURTH AVENUE Copyright, 1913 BY LEA MCILVAINE LUQUER LANCASTER PRESS, INC LANCASTER, PA. PREFACE TO FOURTH REVISED EDITION, 1913. This edition is practically that of 1908, with necessary minor revisions and corrections, especially the data referring to indices of refraction and strength of double refraction. The values of the refractive indices α and γ are recorded as well as the mean values. References are also given to “The Methods of Petrographic-Microscopic Research,” by F. E. Wright, 1912, for exact (quantitative) methods of determining crystal constants. LEA MCI. LUQUER. DEPARTMENT OF MINERALOGY, COLUMBIA UNIVERSITY, NEW YORK, May, 1913. PREFACE TO THIRD REVISED EDITION, 1908. The 1908 edition is essentially the same as that of 1905; the only changes being in the nature of corrections, and the addition of a brief description of the Schrœder van der Kolk method of determining refractive indices and also an abbreviated diagram for determining triclinic feldspars in sections showing both Carlsbad and Albite twinning. The Naumann symbols for crystal forms have also been omitted. LEA MCI. LUQUER. DEPARTMENT OF MINERALOGY, COLUMBIA UNIVERSITY, NEW YORK, April, 1908. PREFACE TO REVISED EDITION, 1905. In preparing the revised edition, Chapters I. and IV. have been rewritten and enlarged and the part relating to the determination of the plagioclases has been greatly amplified. Many additions have also been made to Chapter III. and the Becke method, for the determination of the relative indices of refraction of minerals, has been given in detail. Some new and useful tables have been introduced; as tables of refractive indices (mean) and double refraction (maximum). A diagram has also been added, showing the relation existing between strength of double refraction, interference colors and thickness of section.