Organic action could not be deviated in the minerogenic process of sedimentary hematite,stratabound pyrit and siderite. Its forms of expression are different in different condition.
    Organic activities could form hematite stromatolite and framboid pyrite,and the reduction of organism could transform hematite into siderite.
    In the ferruginous stromatolite and concentric laminae of ferruginous oncolite from the Xuanlong area of Northwest Hebei，there are microplant  fossils in  common. They  belong to rudimentarycyanophyta. Their shags are mainly filamentous and partly pinnate. They directly participated in mineralization of iron.