Long‐time, high‐temperature oxidation of dislocation‐free silicon single crystals is observed to result in the precipitation of silicon oxides. Precipitation is found to occur in banded or striated distribution across the oxidized wafers. The distribution pattern assumed by the precipitates is identical to the pattern assumed by shallow, noncrystallographic etch pits observed upon etching the unoxidized wafers. By employing optical and transmission electron microscopy, the distribution, the morphology, and the structure of the precipitates have been examined. The precipitates are distributed in discrete clusters separated by precipitate‐free regions. They have been identified to be a mixture of both α and β crystobalite. The formation of precipitates results in the faceting of the crystal surfaces as a result of the diffusion and oxidation inhibiting effects of the precipitates. The heterogeneous nucleation is postulated to occur at vacancy clusters in the crystals, and models are presented for the nucleation phenomena and to account for the faceting effect of the precipitates.