Vol 54 Iss. 2

In his scientific work, Prof. I.I. Shafranovsky fruitfully combined crystallographic ideas and methods with the interests of mineralogy. Prof. I. I. Shafranovsky invested a lot of labor in the study of zircon, quartz and diamond. A large work devoted to the zircons of the Cherry Mountains was his Ph.D. thesis...

The practical significance of the crystallographic varieties of simple forms deduced by G. B. Bokii [1940] became evident after the derivation of the twin laws.

According to the law of formation of crystal dissolution bodies formulated by W. Goldschmidt and F. Wright [Goldschmidt, Wright. 1904], the angles and vertices on the dissolution body of a crystal correspond to the poles of the faces present during its growth; the edges to the zones of the faces. This law is cited by A. E. Fersman [1955] as a rule by which the forms of crystal growth should be distinguished from the forms of dissolution. In 1958, F. Frank showed that if the dissolution (growth) rate is a function only of the orientation of its surface, then during dissolution (growth) of a crystal, a point on the surface of a given orientation has a rectilinear trajectory directed perpendicular to the surface of the polar diagram of inverse dissolution (growth) rates of the crystal at the corresponding point.

The relation between plastic deformation of a crystal and mechanical impact is unambiguously established by means of symmetry.The shape of impact or pressure is the deformation at a point. The symmetry of a resting point, according to A. V. Shubnikov, is equal to ∞/∞ m, and the symmetry of a point moving in one direction is equal to ∞ m. The polar vector possesses such symmetry. The stress on the face produced by this vector can be equivalently described by a two-dimensional polar tensor with symmetry ∞ m.

Zircon is an important mineral and one of the most common accessory minerals of igneous rocks. It has been studied in many different directions. Some researchers are trying to use accessory zircon to correlate granitoid massifs, others - to clarify the magmatic or metasomatic way of formation of granites, others see in zircon the key to clarify the sources of demolition.

Quartz is an object of wide and versatile research. To date, much attention is paid to the elucidation of the causes of the various types of coloration of quartz. Researchers are attracted not only by the wide variability of tone and density of coloring of this mineral, but also its special nature, manifested in the discoloration (fading) of quartz when heated and in the restoration or enhancement of coloring when irradiating crystals with X-rays or radioactive rays. The coloration of quartz is associated with electronic processes caused by certain defects in the structure of the mineral.

Crystal accretion surfaces can be referred to the most widespread objects of crystallomorphology, a special case of which are induction surfaces of crystal aggregates.

The results of goniometric measurements of germanium crystals obtained by drawing their melt at different crystallographic orientation of the inoculum are given in the article by G. Novak. In addition, the article by G. Novak shows the dominant morphological role of faces {111} and directions<110>; and <112>;, noted the presence of a number of vicinals and the absence of light maxima from the forms {100} and {110}.

Examining quartz crystals from western North Carolina, A. Gill noted differences in a number of sharp rhombohedra under the faces of the positive {1011} and negative {0111} rhombohedra.

Pegmatite-bearing granite massifs of Kazakhstan are composed of Alaskite granites of essentially potassic (microcline) composition. Pegmatite bodies containing fluorite and quartz crystals are located in granites. Pegmatites, as a rule, have an irregular isometric shape. The size of the bodies varies from 5-10 to 20-25 m in the largest cross-section. According to their internal structure, pegmatites belong to the fully differentiated type. They are composed of a quartz core concentrically surrounded by a blocky, feldspar zone and further by a zone of written granites. Cavities with fluorite and quartz crystals are usually located at the lower contact of the quartz core.

The growth mechanism determines the shape and size of the crystal, the presence of chemical and mechanical impurities in it, and is recorded in the sculptural features of the faces, particularly in the hatching. The most complete summary of the sculpture of crystal faces and methods of its study is given in the last work of V. G. Feklichev. However, most of the methods used to study the facet surface provide a qualitative characterization of the sculpture without evaluating the absolute sizes of its constituent elements.

Vicinal formations on faces {0001} were noted on crystals of Iceland spar from deposits of Eastern Siberia. Crystals of Iceland feldspar belong to different habitus varieties, but they are especially pronounced on samples having the form of truncated dipyramid.