The category of pseudochroism phenomenon also includes the well-known, frequently observed phenomenon of coloring of twin plates growing through calcite grains along the planes of the first obtuse rhombohedron (1012). In this case, the phenomenon of pseudochroism is often very bright for this reason, and also because the position of the twin plates is here easily defined, the phenomenon can be more easily subjected to research. This work represents an attempt at such a study. The application of a “universal” method to the study greatly enriches the picture of the phenomenon and allows us to answer some of the questions it raises. Therefore, I decide to publish the results obtained despite the awareness of the incompleteness of the coverage of the issue.
The following issues are considered in the work: 1. Determination of the value of birefringence from readings with forward and reverse parallel positions of the compensator and the grain under study. 2. The degree of sensitivity of the rotating compensator, the Siedentopf compensator and the quartz and Fedorov mica compensators.
In one of the thin sections of quartz porphyry from the Vtoro-Blagodatny mine, I came across an interesting case of cracks in feldspar grains being filled with feldspathic substance of the same composition and in the same orientation. The rock is quite strongly altered: feldspars are abundantly strewn with muscovite dust. The thin section field is cut by several veins, apparently made of new growths. Moreover, depending on whether the vein cuts through the ground mass or feldspathic segregations, it is made either by an aggregate of feldspars and quartz or only by feldspars, with such a slight difference in orientation with the mineral of the grain cut through by the vein that it cannot be quantified. Feldspar veins are characterized by significantly greater transparency due to the absence of muscovite inclusions.
The purpose of this short note is to publish several new devices and techniques that I introduced during my work on the universal optical (in common speech Fedorovsky) method of microscopic research and which have been already recognized by persons who use this method in their work: 1) segments in a metal frame; 2) rotating comparator; 3) measuring the thickness of a thin section using cracks and inclusions in it by tilting the specimen; 4) hemisphere for graphic solutions to problems of the universal optical research method.
