Abstract: Based on the study of tile geological features, the genesis of Tangshan bentonite deposit on the outskirts of Nanjing is eclucidated and its physiec-chemical properties are investigated. The original rocks of the mineral deposit are rhyolite and tuff. Due to hydrotherma1 alteration under proper conditions the ore can be formed. It is also shown that the bentonites are calcareous ones. After proper ore dressing, the ores can be used for deep procession.