Pyrite, a common mineral in sedimentary rocks, was studied in the Es3x shale of the Eocene Shahejie Formation in East China. Researchers used various methods to analyze the pyrite, finding it ranged from 1.4 to 11.2% in the shale. Different types of pyrite were identified, suggesting the environment during shale deposition was oxygen-deprived. The presence of smaller pyrite crystals indicates a lack of oxygen in the water column. This study helps understand how pyrite forms in shale and the conditions during its deposition, which can be useful for studying similar rocks in other parts of the world.