Elements of mineralogy. Emphasizing the variations in minerals / Элементы минералогии. Подчеркивая различия в минералах

One purpose of this book is to advance the idea that many minerals are not fixed and simple in composition. Some years ago Professor D. Jerome Fisher of the University of Chicago pointed out that the writer's Elements of Optical Mineralogy had made such a treatment available to advanced students for some years, but that no elementary textbook, in any language, presented the subject in a similar way. A result of Dr. Fisher's suggestion has been the preparation of this volume.

About forty years ago, prominent petrographers like Fouque did not accept the idea of continuous variation in composition from one formula to another for any mineral—not even for plagioclase. Perhaps the chief supporter of the idea at that time was the famous mineralogist of Vienna—Tschermak.

Ten years later, Bowen1 proved that artificial plagioclase is a continuous series from one formula to a different one. Still ten years later this theory was accepted as possible for many minerals; Larsen and Glenn2 used it in their study of melanterite and chalcanthite.

The development of the concept that many minerals vary considerably in composition (and properties) is illustrated by the fact that the first edition of the author's Elements of Optical Mineralogy in 1909 contained graphs correlating such variations for only two minerals (plagioclase, then called a series of minerals, and orthoclase-celsian); the second edition in 1928 contained thirty-nine such diagrams; the third edition in 1933 contained fifty-six; and this book contains sixty-three, although it deals only with the common minerals.

Great variations in the composition and properties of minerals are now accepted by  all mineralogists,  but many still cling to the old idea of a simple and (nearly) fixed composition for each mineral. In order to recognize the continuous variations, they tend to create a whole series of names for the different (arbitrarily defined) portions of a continuous series or system, and to consider that each name is that of a distinct mineral. Such names are useful in some cases, but to consider that each name is that of a distinct mineral makes it increasingly difficult, if not impossible, to define a mineral satisfactorily. It seems clear to the author that a single name is needed to designate the whole of any continuous series or system, and that it is desirable to consider that the name designates one mineral (of which there may be many varieties). The extent of possible variations in composition is unknown in some cases, but the variations of most of the common minerals are all known, at least approximately. Moreover, whether the extent of the variation is known or not, it is important that even the beginning student should understand that such variations are common.

In applying this idea of variations in composition and properties to all minerals, it has seemed necessary to use some new or unfamiliar names for certain minerals; but such names have been kept to a minimum, and the familiar names also are used as designations of end-members.

The author acknowledges gratefully the cooperation of his colleague, Professor R. C. Emmons, who offered valuable suggestions for the preparation of the Determinative Tables. He is likewise indebted to Erwin J. Lyons of the Wisconsin Institute of Technology for useful suggestions for the chapter-on crystallography. Professor N. E. A. Hinds of the University of California suggested that X-ray studies of crystals should be described. Finally, the author is indebted to his son, Dr. Horace Winchell, crystallographer of the Hamilton Watch Company, for valuable contributions to the chapter on crystallography, especially the description and use of the Hermann-Mauguin symbols. He appreciates highly the courtesy of John. Wiley & Sons, publishers of Elements of Optical Mineralogy, who allowed him to use freely many paragraphs and illustrations from that source.