Until now, a number of important general questions concerning the conditions of formation of quartz veins and crystal nests developed within the crustalenous fields remain to some extent debatable.

Over time, more and more examples of rational interpretation of ore field structures have been accumulated, which significantly helps further prospecting and exploration works. Over the last ten years, the intensified development of this problem has also begun in application to crustaleniferous fields. Undoubted progress has already been achieved for the fields of crystal-quartz veins (works by A. E. Karyakin, V. A. Smirnova and others in the Subpolar Urals). Deciphering of the structures of the fields of crustalene pegmatites has not yet been completed and there is no unanimous judgment on the methodological basis necessary for this ...

Pegmatite fields confined to the zone of development of Hercynian granitoid intrusions on the eastern slope of the Urals have been studied, as is known, for a very long time. To a large extent, these pegmatites are among those natural objects on the example of which the classical theory of the genesis of pegmatite formations is built ...

It is known that in the Mamsko-Chuyskaya pegmatite province - the main supplier of industrially valuable large-crystalline muscovite - there are several types of mica deposits, different in the form of ore bodies, structure and geological conditions of occurrence. Among them, of special interest are mica-bearing zones developed in large bodies, mainly composed of granite-pegmatite material. The bodies of these rocks are found in gneisses and crystalline schists in the form of isolated interlayered deposits and secant dykes or form a suite of converged interlayered deposits connected by a network of secant apophyses. N. V. Petrovskaya called such formations of convergent bodies of granite-pegmatite separated by interlayers of metamorphic rocks giganto-migmatites ...

The problem of rare-metal mineralization of pegmatites is an object of lively discussion. One group of researchers, mostly sharing the genetic ideas of A. E. Fersman, continues to defend the idea of the existence of a specific “pegmatite melt-solution”. It is assumed that the main mass of rare-metal compounds was contained in this “melt-solution” during its introduction into the host rocks. The formation of pegmatites (and rare-metal minerals in them) is represented as a process of successive crystallization of the melt, sometimes accompanied by autometasomatic transformations of early crystallization products under the influence of still liquid residue. The possibility of new portions of postmagmatic solutions entering the crystallizing pegmatites is admitted. However, the participation of these solutions in the occurrence of rare-metal mineralization seems to be limited.

Thanks to the outstanding studies of pegmatites made by A.E. Fersman, a group of his collaborators and followers, which aroused general interest in this important type of mineral deposits, as well as the works of numerous foreign scientists, the hypothesis of pegmatite formation by fractional crystallization of the so-called “pegmatite” melt was almost universally accepted among Soviet geologists for many decades. The hypothesis was based on the idea of successive crystallization of this melt in a calm tectonic environment, in a closed and isolated chamber of the pegmatite vein body. It was assumed that rare-metal minerals and large-crystalline mica, as well as minerals of the accessoria (garnets, apatite, tourmaline, etc.) appeared by crystallization in the free environment of the “pegmatite melt” before the surrounding quartz-feldspar rocks of the pegmatite crystallized. It was supposed that in some cases some of the rare-metal minerals could also arise as a result of autometasomatic reactions under the influence of the so-called “residual solutions” separating from the “pegmatite melt” here on the spot, inside the vein chamber.

Graphic granites by the peculiarity of their structure have long attracted the attention of researchers. It is known that these rocks are similar to ordinary granites in their chemical and mineral composition, but all the quartz in them is enclosed within feldspar crystals in the form of numerous correctly oriented inclusions. The latter often resemble the pattern of ancient graphics. This peculiarity of the rock structure determined their name: runites, Hebrew stone, graphic pegmatites, pegmatite and the most accepted in our literature - graphic granites. Graphic granites are part of various geologic formations. They are known in dikes of acidic igneous rocks, in the apical parts of granite massifs, as part of strata of deeply metamorphosed rocks such as gneisses and others. The most spectacular and coarse-grained samples of written granites are found in pegmatite veins. It was here that they were studied in detail, and their first descriptions are more than a century and a half old. Since then a great deal of work has been devoted to the study of graphic granites and especially to a discussion of the genesis of these rocks.

Such minerals as muscovite, feldspars, ores of a number of valuable metals - lithium, beryllium, partly niobium, tantalum, elements of the rare earth group, etc., are mostly extracted from pegmatite deposits. The industrial significance of pegmatite bodies is constantly increasing. Pegmatites, in addition, are often receptacles of many rare minerals, and in some cases serve as natural museums of beautiful crystals, which attracts the special attention of mineralogists. The peculiarity of the genesis of pegmatites has long been of interest to petrologists and geochemists. In the phenomena of pegmatite formation, researchers encounter perhaps the most complex process of mineral formation, with which one can perhaps compare only the process of skarn formation. When studying pegmatites, the interests of petrologists and mineralogists are closely intertwined. In pegmatites, phenomena that indicate the general features of various processes of mineral formation and transformation of the rocks that make up the veins are manifested with such exceptional clarity and on such, often, enormous scales that in other types of deposits they are generally unknown or are discovered in a much less clear form.

As is known, there are many works on the issues of pegmatite genesis, including the processes of formation of large muscovite crystals in them. Despite this, various researchers until very recently have very contradictory opinions on a number of the most important patterns of mica formation. Therefore, the ideas about the patterns of spatial distribution of muscovite in pegmatite rocks, about the nature of the distribution of mica mineralization to depth, etc. are also contradictory. The absence of a definite solution to these main practical issues in a number of cases complicates the correct choice of methods for the prospective assessment of veins, exploration and exploitation of muscovite deposits. Let us recall that at present there are the following ideas about the genesis of large muscovite crystals.

As a petrologist of the geological expedition of the Central Asian Geological Administration, the author studied the Kirghiz and Talas Ala‑Tau ranges from the meridian of the village of Dmitrievskoye in the west (72°15′ east longitude from Greenwich) to the meridian of 73°45′ in the east. The region of the Kirghiz and Talas Ala‑Tau mountain ranges from the meridian 72°15′ east longitude from Greenwich in the west to the meridian 73°45′ in the east consists chiefly of various Proterozoic and Lower Paleozoic metamorphic shales, quartzites and marble limestones. Less developed are the Lower Silurian limestones and the so‑called “Toluk” tuffaceous‑limestone sequence of the Lower and partly Upper Silurian. The enumerated sequences are intensely dislocated and cut by enormous granite, diorite and other intrusions. On the above‑mentioned rocks, unconformably with them, lies the Lower Carboniferous sequence of red‑colored sandstones and conglomerates, containing in its lower part a limestone bed 70–500 m thick with abundant fauna. Above this lies the red‑colored sequence of arkose and tuffaceous sandstones and conglomerates — the so‑called “Aramin” sequence. All the above‑mentioned sequences are covered, unconformably with them, by Tertiary variegated formations.