Investigation of the Effect of Iron and Mechanical Milling on the Carbothermic Reduction of Molybdenite in the Presence of Lime In this study, the effect of iron and mechanical activation on structural evolution and reduction behavior of molybdenite, with Carbon in the presence of Lime has been investigated. Various iron amounts (0-10%wt) were added to the powder mixture of molybdenite, carbon and lime (1:2:2). Mechanical milling was performed on the mixtures in argon atmosphere for different time periods (0-70 hours) , using a planetary ball mill.Phase determination was carried out using a X-Ray diffractometer with Cu k ? radiation (?=1.5405 A o ). The results demonstrated that by 70 hours milling on activated powders with and without iron, no chemical reaction occured in the mixture. XRD analysis revealed that carbon peaks completely disappeared in diffraction patterns of samples milled for more than 10 hours, due to the annihilation of carbon crystal structure. In addition, change in molybdenite crystallite size and structural microstrain were studied based on integral breadth analysis of obtained XRD patterns. However, by mechanical activation the grain size and structural strain of molybdenite were decreased and increased, respectively. Furthermore, iron content had no influence on molybdenite,carbon and lime mixture activation.More over scanning electron microscopy (SEM) was carried out in order to investigate the morphological changes in the structure due to milling. SEM observations revealed that mechanical milling produsces a compacted composite structure of particles. The mechanical activation parameter (?/d) was introduced for evaluation of mechanical activation and also as a criterion for the degree of mechanical activation in different mixtures.The obtained results from the methods were in agreement with previous findings. The effect of milling time and iron content on the reduction of different samples were thoroughly investigated by Simultaneous Thermal Analysis (STA). The samples were heated in argon atmosphere with the linear heating rates of 10, 15, 20 o C/min. The plots of process conversion degrees versus temperature showed that