Quartzites are widespread within Earth’s lithosphere, but their highly pure varieties occur quite infrequently. With the development of alternative energy sources, including solar, and with increasing demand for high-purity quartz for optics, interest has risen in high-purity silicon-bearing materials. The quartzites discovered in the southeast part of the Eastern Sayan Mountains are particularly attractive for exploration in terms of their raw material quality and feasibility to be enriched. For this reason, their genesis also merits study. Available geochemical data show that chemogenic (d¹⁸O > 29.2‰) siliceous-carbonate sediments of the Irkut Formation are fairly pure (impurity elements < 800 ppm), and that half the impurities are easily removed carbonate components of the rock. Bedded quartzites remote from the intrusive granitoids and near-contact quartzites were recognized based on geochemical and petrographic data. Influenced by the Sumsunur granitoids, the near-contact quartzites originally contained > 0.9% impurities, but later, under the action of sliding slabs of ophiolite dynamothermal treatment reduced impurities to < 100 ppm, resulting in “superquartzites” (highly pure quartzites). The presence of only minor structural impurities is due to the enrichment capacity of superquartzites to 10.1 ppm (7.2 ppm under special conditions) of 10 elements: Fe, Al, Ti, Ca, Mg, Cu, Mn, Na, K, and Li.