Scientific publications

The article reports the first ever detailed study of rose pegmatite quartz from the Pirtostrov occurrence in the Loukhsky District of Karelia. Rose quartz, together with white and smoky quartz varieties, forms large blocks within the pegmatite veins of the deeply metamorphosed Khetolamba complex, which consists of amphibolites and amphibole gneisses. The quartz forms dense granular aggregates in the veins and has a translucent structure with numerous fine cracks. Optical and scanning electron microscopy, powder X-ray diffraction, Raman spectroscopy, and inductively coupled plasma atomic emission spectrometry were used to identify the quartz petrographic and structural features and determine its trace element composition. Microscopic methods revealed micromineral inclusions of feldspar, muscovite, and calcite, as well as numerous, randomly oriented acicular inclusions approximately 0.5 μm thick, identified by Raman spectroscopy as the borosilicate mineral dumortierite Al₇(BO₃)(SiO₄)₃(O,OH)₃. According to research, submicroscopic dumortierite inclusions in massive rose quartz from granite pegmatites in various regions of the world are responsible for the rose coloration. The results of ICP-AES trace-element analysis of quartz from the Pirtostrov occurrence indicate elevated boron and aluminum levels, suggesting a possible presence of aluminum borosilicate inclusions in the quartz matrix. Dumortierite is supposed to have formed in pegmatitic quartz during the final stages of acid magma evolution, when residual hydrothermal fluids enriched in silicon, aluminum, and boron crystallized under decreasing temperature and pressure. Under high temperature conditions, the quartz crystal lattice captures trace elements, and as the pegmatite body cools, it contracts, forcing these elements into the intercrystalline space, where crystallization centers for a new microscopic phase nucleate. Ironand magnesium-deficient conditions inhibited the growth of tourmaline (schorl) and favored the synthesis of dumortierite.