**Abstract**

Super-large quartz sandstone deposit has been discovered in Northeastern Yunnan and the major ore-bearing bed is occurred in the Member 1 of the Middle Devonian Suotoushan Formation. Systematic study on the sedimentary characteristics of the Suotoushan Formation in Yiliang region, northeastern Yunnan Province has been conducted, Profile surveying, drilling and trenching show that, microscopic identification, the thickness of the Suotoushan Formation is 62.8 m 222.7 m and principally composed of gray-white thick-bedded medium-grained quartz sandstone with well developed parallel bedding, swash bedding, oscillation cross-bedding and wave ripple, showing remarkable wave action features. Thin section observation shows that quartz sandstone in the Member 1 of the Suotoushan Formation is grain supported, siliceous cemented, concave-convex and line contact and the pressure solution and secondary overgrowth of quartz sand grains are obvious. Grain size analysis shows that the grain size is concentrated between 1.5Φ and 3.5Φ with saltation population up to 99% which is composed by tow sub populations and lacking of traction and suspension populations, showing a typical foreshore grain size distribution. Chemical analysis shows SiO2 chemical purity of the quartz sandstone is 99.05 99.39 with weighted average 98.99 (N = 11) which has exceeded the industry standard for first-grade raw material of plate glass. Based our studies above, it can be concluded that the quartz sandstone in Member 1 of Suotoushan Formation is high energy coastal foreshore sediments with high texture and mineral maturity, and has been further purified by diagenesis, and both the grainsize characteristic and chemical purity have reached the standard of high-purity quartz sandstone, which can be expected raw material for high-purity quartz. The results in this article can provide accurate prospecting target to enlarge the resources potential of high-purity quartz deposits in northeastern Yunnan.

**Keywords:** Northeastern Yunnan, high-purity quartz sandstone, Middle Devonian, Suotoushan Formation, foreshore
