Search signs for crystal nests in the Subpolar Urals

Abstract

Even a cursory review of the geological map of the Crystal Belt of the Subpolar Urals leads to the conclusion that numerous deposits of piezo-optical quartz are localized in the metamorphic strata of the Proterozoic and Lower Silurian, and in the northeast are quite clearly delineated by outcrops of the third formation. It should be noted that the lower formation is composed predominantly of mica schists, the middle - of quartzites, and the upper - of limestones. Consequently, the partitioning of the metamorphic strata of the Subpolar Urals characterizes not only the relative age of the formations, but also the peculiarities of the chemical composition of the rocks. Therefore, within the crustal band stratigraphic search features are inseparably connected with lithologic ones. In addition, the dependence of the mineral composition of crystal nests on the chemistry of the host rocks is quite definitely outlined even on a regional scale: essentially quartz rocks - Proterozoic shales and quartzites of the Lower Silurian are saturated with nests with quartz crystals, while limestones of the Upper Formation do not contain crystal vaults.