A batch of coke samples were extracted from the lower zone of a European working blast furnace through tuyere drilling. Mineral matter of coarse coke lumps (+19mm) from several locations from the furnace walls were characterized using XRF, SIROQUANT and Scanning Electron Microscopy (SEM). This paper quantifies mineral phases of lower zone coke with particular focus on transformation of silicon (Si) bearing minerals. The implications of silicon carbide (SiC) formation on coke properties are also discussed.