Microscopic investigation indicate that pyrrhotites in the Meixian and the Qianfeng massive sulfide deposits are mostly synsedimentary in origin and have suffered metamorphism of greenschist facies and deformation of various degrees in the geological history since their fromation. Coating with magnetic colloid has revealed intergrowths of monoclinic pyrrhotite (mpo) within hexagonal pyrrhotite (hpo) grains. These intergrowths include two morphological types: crystallographically controlled lamellar patterns and fissure-and grain boundary-controlled irregular patterns. Lamellar intergrowth of mpo is produced by exsolution from hpo as a consequence of cooling of hpo from emperatures exceeding 254℃, whereas irregular intergrowth results from eplecement of hpo by mpo. The exsolved mpo lamellae have suffered late-stage deformation and metamorphism, resulting in coarsening and homogenization represented by wedge-shaped boundaries, boxwork shapes and complex internal textures. The deformation of sulfide ores in the Qianfeng deposit appears stronger than that in the Meixian deposit, which is evidenced by ubiquitous textures such as subgrains, mechanic twins,kinkbands, and annealing triple junctions and core-mantle assemblages. Mpo lamellae are well preserved in less deformed pyrrhotite either in Meixian or in Qianfeng, but is mostly erased in intensely deformed grains in the Qianfeng deposit, suggesting that anisotropic stress during annealing tends to enhance homogenization of the intergrowths to form uniform hexagonal grains.