**5. Chemical purity**

Chemical purity is one of the evaluation factors of high purity quartz sand [1], and also a standard to measure whether it meets the plate glass industry index [12]. In view of this, the chemical composition of quartz sandstone in the first and Member 3 of Suotoushan Formation in the study area was analyzed (**Table 2**). The analysis results show that, except for a small amount of Fe2O3, the SiO2 index of the Member 1 of Suotoushan Formation quartz sandstone exceeds the standard of the first grade industrial index for flat glass, while the Fe2O3 and SiO2 quartz sandstone of the Member 3 of Suotoushan Formation basically cannot reach the standard of the first grade. Therefore, the Member 1 of Suotoushan Formation is a favorable horizon for high purity quartz sandstone deposit.
