Interesting samples of potassium feldspars in the Museum of the Mining Institute

Abstract

First of all, interest was aroused by the huge Bavinsky twin of orthoclase from the vicinity of Kyakhta, depicted in Fig. 1, and not only by the clarity of its formation, but also by the beautiful almandive crystals included in it. A special optical study carried out by V.I. Sokolov showed that the orthoclase substance is germinated by plapoclase around No. 5, representing well-formed polysynthetic twins according to the albite law, and one individual of the twin is concordant with the orthoclase substance.