Vol 38 Iss. 2

A universal geometrical doctrine of crystal shapes of both ordinary and complicated crystals (crystal skeletons, growth pyramids, induction surfaces, regular aggregates, etc.) has now been completed.

The present communication completes the series of articles by V. I. Mikheev and I. I. Shafranovsky devoted to the complete derivation of all possible edge forms. In the derivation of simple edge forms of the cubic system, we first of all proceed from possible facet combinations. For this purpose we had to enumerate all possible pairwise combinations separately for each of the five kinds of symmetry. The symbols for such combinations are summarized in the table, where the upper horizontal line contains the symbols of the faces of the initial forms, in the planes of which lie the derived edges. The vertical line contains combinations of symbols of those faces, the intersection of which results in edge forms. A number of edge forms with a relatively small number of included edges are the result of intersection of faces of one simple form (from among those indicated in the upper horizontal row of the table); for example, the dodecahedron of the cube.

Two polymorphic modifications of iron oxide hydrate are known in nature – goethite α‑FeO(OH) or HFeO₂ and lepidocrocite γ‑FeO(OH). However, until now in the literature and practice, the name hydrogoethite is common for loose ferruginous formations, which, according to E. Ya. Rode and B. K. Brunovsky, represents a solid solution of zeolite‑type water in goethite. The presence of such water should cause an increase in the interplanar distances and, consequently, in the unit cell parameters of the so‑called hydrogoethite (the same applies to hydrohematite). But, as X‑ray diffractometric studies show, the changes in the values of interplanar distances are so insignificant that they are within experimental error. Such loose formations, apparently, are finely dispersed goethite containing a considerable amount of adsorbed water. Debye patterns of hydrogoethite differ from ordinary goethite only by strong blurriness and width of the diffraction lines.

Simple edge forms of trigonal and hexagonal syngonies. For crystals of trigonal and hexagonal syngonies we have derived 90 simple edge forms. In order to classify them, we will use the numbering and special symbols adopted for tetragonal forms.

At present, work is underway to compile an X‑ray diffractometric determinative guide of metals and alloys. For each crystalline substance, a characteristic X‑ray diffraction pattern is determined. The study of diffraction patterns makes it possible to identify identical substances and distinguish between different ones. The process of determining substances consists of obtaining and calculating the diffraction pattern, and then comparing the results with previously taken reference diffraction patterns of known substances. The set of reference diffraction patterns of metals and alloys will constitute the X‑ray diffractometric determinative guide of metals and alloys.

Several samples of schlich platinum from a differentiated gabbro-diabase intrusion located in the Taimyr National District were studied. The schlich platinum was preliminary divided into three fractions: electromagnetic (EMF), magnetic (MF) and strongly magnetic (SMF).

Nineteen samples of ilmenite were studied (Table 1), of which one sample 436a was a crichtonite, i.e., ilmenite almost free of magnesium, from a differentiated trap intrusion on the Alamzhakh River, and the remaining 18 samples were collected with the help of an electromagnet from crushed kimberlite from the Zarnitsa and Mir diamondiferous pipes (Yakutia). From crushed ilmenite, individual fractions were sampled at different current strengths in the electromagnet in the range 0.4‑1.2 A every 0.1 A. Two such series of samples of 9 fractions each were selected. The first series from I‑1 to I‑8 and I‑19 is represented by ilmenite from the “Mir” pipe, the second – from I‑9 to I‑28 from the “Zarnitsa” pipe. Specific gravity was determined for all selected fractions.

The following tasks were set before the X‑ray diffractometric study: to establish amorphous or crystalline nature of samples; to find out whether there are significant structural changes for different samples of gummites, isolated by morphological features into varieties; to identify, if possible, the reasons for the structural features of different samples; to give X‑ray diffractometric standards for gummites, comparing them with the results of X‑ray diffractometric studies of these minerals available in the literature; to trace the nature of changes in minerals during their heat treatment. The work was carried out in the X‑ray diffractometric laboratory of the Fedorovsky Institute at the Leningrad Mining Institute in 1948.

The X-ray laboratory of the Leningrad Mining Institute, headed by V. I. Mikheev, systematically carried out studies to determine the material composition of various products and mineral formations. These works were carried out at the request of various industrial and scientific organizations.

When studying the scientific works of V. I. Mikheev, one is first of all struck by the exceptional purposefulness and clarity of the main line of his work. This line is a direct continuation and development of the works of his teacher A. K. Boldyrev, and thereby the works of E. S. Fedorov. That is why in our eyes V. I. Mikheev is an outstanding representative of the Fedorov school, the crystallographic-mineralogical school of the Mining Institute. In order to trace the defining features of V. I. Mikheev's creative path, it is necessary to recall some characteristic moments from his biography.