FIELD: inorganic compounds technology. SUBSTANCE: charge constituted by SiO2 particles is heated in reactor with vertically-oriented central axis and then subjected to gas- treatment. Gas is fed into reactor and charge is loaded bottom-up with predetermined flow velocity. Treatment gas contains chlorine. In the region of charge, treatment gas temperature is adjusted to at least 1000 C and flow velocity at least 10 cm/s. In apparatus, gas-supply gas shower is mounted, which has, under the charge, a large number of nozzle openings distributed peripherally to central axis. Purified silicon oxide particles from natural- origin raw material are characterized by contents of (wt. %) iron less than 20•10-7, preferably less than 5•10-7, manganese less than 30•10-7, preferably 5•10-7, lithium less than 50•10-7, preferably 5•10-7, and also chromium, copper, and nickel each less than 20•10-7, preferably 1•10-7. EFFECT: enabled preparation of higher-purity of SiO2 particles suitable for manufacturing blanks or finished quartz glass products. 20 cl, 2 dwg, 1 tbl
