An experimental study was conducted to establish the effect of two different carbonization conditions on mineral phase changes, in particular, iron-bearing minerals, and coke properties such as carbon crystallite height and micropore surface area. Coal and coke minerals were characterized using QEMSCAN, XRD and SEM/EDS. Reactivity of coke to CO2 was carried out using a fixed bed reactor under chemical-controlled conditions. Under all the tested carbonization conditions, pyrite, siderite and Fe-rich clay minerals in coal were transformed to iron-sulfides, metallic iron and some amorphous material, which on gasification by carbon dioxide were transformed to iron-oxides, dominantly magnetite. In coke prepared in both small scale and larger scale systems, the apparent reaction rate initially increased with increasing amounts of the catalytic iron minerals, but at high iron contents the rate was insensitive to the amount of catalytic iron. However, the maximum apparent rate was different for coke prepared in the different ovens. In cokes with similar iron content, the reactivities of the cokes varied greatly with carbonization conditions; most likely due to the effect of carbonization conditions on surface area and carbon structure.