(1) (a) Les méthodes de Fédorof et leurs applications a la détermination des plagiodases (2) Mikroskopische Physiographic der petrographisch-wichtigen Mineralien

Abstract

THE employment of crystal optics in the determination of minerals is a very special branch of applied physics which has been industriously pursued in recent years, but it is the task of distinguishing between the different plagiodases that has called for the greatest refinements. These important constituents of igneous rocks present the closest resemblance to one another, but vary greatly in composition, forming a continuous series from albite, soda plagioclase rich in silica, Na₂OAl₂O₆SiO₂, to anorthite, lime plagioclase, CaOAl₂O₃2SiO₂, which contains much less. They differ, however, in the orientation of their axes and planes of optical symmetry relatively to their crystal structures, and in other optical characters. The foundations of these investigations were laid by Schuster, in Germany, and Michel Levy in France, but it is to the great Russian crystallographer Fedorov and his pupil Nikitin that we owe the latest and most far-reaching developments, and they have now been rendered generally available by Duparc and Reinhard in Switzerland, and by Wiilfing in Germany, in the works before us.

(1) (a) Les méthodes de Fédorof et leurs applications a la détermination des plagiodases.

Bull. Suisse de Minéralogie et Pétrographie, tome iii. fasc. 1–2, par L. Duparc et M. Reinhard., 1923. (b) La détermination des plagioclases dans les coupes minces, Mémoires de la Société de Physique et d'Histoire naturelle de Genève, vol. 40, fasc. 1, par L. Duparc et M. Reinhard, 1924.

(2) Mikroskopische Physiographic der petrographisch-wichtigen Mineralien.

Begründet von H. Rosenbusch. Band 1. Erste Hälfte: Untersuchungsmethoden. Fünfte, völlig umgestaltete Auflage, von Prof. Dr. E.A. Wülfing. Zweite Lieferung. Pp. iv + 253 532. (Stuttgart: E. Schweizerbart's che Verlagsbuchhandlung G.m.b.H., 1924.) n.p.