Book Description

Excerpt from The Constitution of the Silicates From what may be called the natural history of a mineral, still another group of data can be drawn, relating to its genesis, its con stant associations, and its alterability. In this connection pseudo morphs become of the utmost interest, and, properly studied, shed much light upon otherwise obscure. Problems. An alteration product is the record of a chemical change, and as such has weight-y signifi cance. The decomposition of Spodumene into eucryptite and albite, the transformation of topaz into mica, and many like occurrences in nature, are full of meaning with reference to the problem now under consideration. Just here, however, great caution is necessary. Min era-logical literature is full'of faulty records regarding alterations, and many diagnoses need to be revised. Pseudomorphs have been named by guesses, based upon their external appearance, and often a com pact mica has been called steatite or serpentine. In every case an alteration product should be identified with extreme care, both by chemical and by microscopical methods; for without such precautions there is serious danger of error.' In each instance the supposed fact must be scrupulously verified. Closely allied to the study of natural alterations is their artificial production in the laboratory. The transformation of leucite into anal cite, and of analcite back into leucite, is a case in point, and the admi rable researches of Lemberg furnish many other examples. Work of this character is much less difficult than was formerly supposed, and its analogy to the methods of organic chemistry renders its results highly significant. Atoms, or groups of atoms, may be Split off from a mole cule and replaced by others, and the information so gained bears directly upon the question of chemical structure. With evidence of this sort relations appear which could not otherwise be recognized, and these relations may be closely correlated with observations of natural occur rences. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.