A lot of perfect ornamental Three Gorges landscape stones found in Eastern Three Gorges Area. They are actually large scale calcium(silica) syndepositional nodules body wrapped in sedimentary rocks. Through studing the field character, internal composition, forming environment and other aspects of thses rocks.The paper points out that they came into being probably in strong reducing shallow shelf stagnation flows (the Gulf) basin with very stable hydrodynamic conditions. Referring to the report “experimental and synthetic manganese mineral products” and “crystal nucleation theory” as well as recent research insights of foreign scholars, we shows a comprehensive in depth analysis and discussion on formation mechanism of the sort of rare syngenetic concretion.