Vol 2 Iss. 3

The work that was carried out this summer in the platinum-bearing area was aimed at finding out in which direction exploration for primary platinum should be carried out. The only goal in our work was to collect material for the petrographic characterization of the area. Samples were taken from outcrops mainly along neighborhood clearings, roads and ravines. The results of processing the collected material represent the bulk of this work. In another part I will focus on the discovered platinum deposits.

In this article, I narrow my task to the highest degree and do not even mention the various geometric systems and their combinations that make it possible to solve it; I focus exclusively on considering one single system of the 4th stage on the plane, which most directly corresponds to the essence of the matter. This system is a direct extension of the system of parallel vectors, namely, it is expanded in the sense that vectors, as elements of the system, do not have to be taken as parallel. It is clear that through this condition the system increases by a step, that is, it becomes precisely a system of the 4th step (corresponding to the geometry of the space of 4 dimensions).

In spring 1907 and 1908 the authors of this note participated in a geological excursion along the northern coast of Lake Ladoga. The excursion began with an examination of the Imatra waterfall and the surrounding rocks with characteristic signs of the Ice Age. From Imatra we drove to the city of Serdobol and from here we set off on foot along the shore of Lake Ladoga, getting acquainted along the way with the rocks of this area and with two ore deposits, Velimeki and Pitkaranta, which was the final destination of our trip. Without having in mind a description of all the material, for our brief note we selected only rock samples that we took along the way from the town of Serdobol to the Velimeki iron mine inclusive, the most interesting from a petrographic point of view.

In the summer of 1901, I managed to inspect the Kerch mines, where I obtained a fragment from a large piece of barite with the date that it was found in a mine located near the plant. The piece in its original size was about 2 kilos in weight and had the shape of a mushroom; completely dense both in its central part and at the edges; waxy yellow with a white line, translucent in small pieces and transparent in thin fragments; the pereferical layer is about 3 mm thick. yellowish-white, cloudy. The structure is radiant. March 20, 1909

The presence of vesuvianite, this characteristic contact mineral, together with garnet, makes the rock particularly interesting from the point of view of the genesis of the Magnetic Mountain ore deposit. It is hardly possible to attribute a hydrochemical origin due to weathering processes to such a rock as described; on the contrary, we see clear traces of contact metamorphism in it.

A hemisphere with a radius of 5 mm was cut out of a soldered piece of calcite. with a diametrical plane (110) (plaques, cleavages). This hemisphere, glued with wax to a glass hemisphere of the same diameter, was suspended by a thread in a supersaturated NaNO3 solution. Previously, to clean the surface of the calcite hemisphere, the ball glued together in the above manner was immersed in a weak hydrochloric acid solution for several seconds.

The crystals of this mineral from the museum of the Mining Institute have already been systematically described by me in a special article. Recently, the museum has received two new interesting crystals of this mineral. What is most striking is their extraordinary thinness, reaching up to 0.1 mm with a planar size larger than a square. centimetre. With such extreme differences, it is especially instructive to raise the question of the existence of a relationship between a form and a combination.

A. E. Kupffer, crushing the rock from San Zenito in California, which contains almost black and rather large neptunite crystals in abundance, isolated, among other things, an excellently formed crystal of a rather dense blue color, developed in combinations of a typical rhombic crystal with four very sharp pyramids (see the article).

Using the hemispheres of potassium alum that I had and the corresponding depressions in a large crystal, I wanted to test how impurities in the solution, which do not have a decomposing effect on the substance contained in the solution, affect the same crystallization. A likely conclusion is the formation of faces, although of poor quality, with more complex symbols on spherical surfaces, but of such small magnitude that reflexes are generally imperceptible, and only some of them begin to become perceptible, due to impurities that improve crystallization.

Vicinaloids or vicinal surfaces are those surfaces that, while forming the true faces of crystals and very close to planes, are actually not planes, but very complex and diverse curved surfaces. But if, in general, during crystal growth, crowding, that is, the non-parallel position of particles on top of each other, occurs chaotically, that is, equally in all directions (complete disorder of crowding), then one cannot deny the possibility of the existence of causes that violate this complete disorder and produce incomplete disorder.

The basis of the modern concept of legality in the formation of facets is the provision on the agreement of the order of importance of facets (manifested both in particular in their appearance and in their magnitude) with the order of their reticular density. This is supposed to be derived from experience as a statistical law, that is, not as an exact law that has always and unconditionally manifested itself, but as legality, which manifests itself in a significant majority of cases. The exceptions that we generally find in experience by no means exclude the idea of the absolute value of the order of the density of faces but they indicate that the formation of faces, in addition to this absolute factor, is influenced by others, the value of which cannot yet be expressed numerically; and these factors can be quite numerous, since the degree of education various external, partly difficult-to-detect conditions also affect one or the other facets.

I would like to note not only the diversity seen from these tables, which is important for crystal chemical analysis, but also the importance of the intermediate minimum that is observed for the main numbers. It should be noted that in isotropic complexes, the difference between tetragonaloid and trigonaloid disappears and, in general, crystals could be classified as pseudocubic. But if we add real cubic crystals to them, then we would get a special cluster of crystals for this particular gap, which would be an unfavorable factor for analysis, and it turns out that just in this gap, some rarefaction in distribution naturally results.