This paper presents the results of further research undertaken to determine the optical symbols of various minerals. A table of individual observations in mica plate is provided. At the end of the article, more detailed data regarding observations in simple and combined plates are provided, as well as the characteristics of individual members of the group under consideration (muscovite, alomite, biotite, phlogopite, etc.).
In the article by Prof. E. S. Fedorov, "Representation of Crystal Structure by Vector Circles," a graphical method is presented for finding the reticular densities of crystal faces (more precisely: the squares of the reticular densities of the corresponding nets). Anyone who has dealt with determining the reticular densities of faces by this method knows that it involves making certain constructions—not particularly complicated, but nonetheless quite time-consuming. This article aims to show how the task can be simplified, reducing the drafting work to a minimum.
A sample of the rare mineral Hambergite from a new deposit on the island of Madagaskar was sent to the Museum of the Mining Institute from the Bohm Mineralogical Office in Vienna. The article presents research data on this rare mineral and a description of the original figures on some cleavage fragments.
From the Museum of the Mining Institute, specimen No. 169/3 labeled: “Bronzite from the Slyudyanka River” was transferred for research to the Mineralogical Cabinet. Two thin sections prepared from it showed that the sample is a rock, which, in fact, contains, as a component, an orthorhombic pyroxene close to bronzite. The rock itself presents some features in its composition and structure, which lead to its classification as a drusite-type rock.
Prof. E. Fedorov proposed a method for determining the nature of the dispersion of optic axes using a universal stage and deriving the optical orientation symbol of a mineral. Currently, at the Mineralogical Institute, a series of measurements have been undertaken using this method. This note presents the results of the first (still limited) observations.
